Only the linesman knows why he did not raise his flag when the Bolton Wanderers substitute received Jay-Jay Okocha's return pass, unmarked and clearly standing offside just eight yards out.
It was a cruel way to lose two points and manager Glenn Roeder said: "It was clearly offside but it's typical of our luck. We're not getting the rub of the green."
Roeder and Joe Cole were also adamant that the young Hammers skipper should not have been denied a clear second half penalty.
"I've never been one to call for the officials to use technology - action replay cameras - to check their decisions but I'm rapidly changing my mind about that. It annoys me that the officials can't do their job and that they are always so adamant that they are always right, when they clearly are not.
"You will not find a more honest player in those situations than Joe - he's not a diver and it was a definite penalty," added the frustrated Roeder, still seeking his first home win of the season after 11 attempts.
What referee Steve Bennett and his assistants couldn't be blamed for, however, was Hammers' failure to add to makeshift striker Ian Pearce's 17th minute opener.
Trevor Sinclair won't want to view his awful miss - a header guided wide of the post from six yards out - in the 88th minute when it's replayed on The Premiership tonight. The England international found himself completely unmarked when Steve Lomas' cross came in from the right, but his diving header somehow dropped just wide with the goal at his mercy.
Sinclair was Hammers' most likely match-winner on a wet and dreary afternoon. He went close in the second half on two other occasions, but Ricardo Gardner stopped him with a last-gasp tackle and then he saw a dipping scissors-volley sail just a yard over.
Pearce again worked hard for his goal, collecting a flick on from Jermain Defoe and cutting inside before beating Jussi Jaaskelainen with a low, right-foot shot from 12 yards. Pearce and Defoe had earlier both missed half-chances, while Lomas headed over from a good position.
Bolton's defence looked in dissaray in the opening 20 minutes but, ironically, after taking the lead, Hammers found themselves under more pressure as the first half progressed. In fact, Wanderers were unlucky not to equalise on 25 minutes, when Henrik Pedersen turned and struck a left-foot shot that rebounded back off the far post.
The visitors' only other bright moment of a gloomy first half came when David James did well to fist away a 25-yard piledriver from Per Frandsen.
Hammers regained the lion's share of possession early in the second period but too often promising moves foundered on the linesman's offside flag. Defoe was the main culprit, repeatedly mistiming runs.
It was a fragile lead, though, and the home fans' fears that a first home win would remain elusive proved the case when Ricketts latched on to Okocha's flick and controlled the ball on his chest before nudging it past the helpless James. Surprisingly, the home players didn't protest too strongly at the time, although a furious Tomas Repka berated the guilty linesman at the final whistle and had to be dragged away by team-mates.
Bolton boss Sam Allardyce was pleased with his side's point, while the only pleasing aspect for Roeder was the long-awaited return of Don Hutchison. Replacing the tiring Pearce up front in the 79th minute, Hutch showed some neat touches in his first senior game for 10 months. Now recovered from knee ligament damage, his experience and ability to score and create goals will be a much-needed boost.
Roeder says he also expects Fredi Kanoute to return for the Boxing Day home clash with Fulham, when Hammers will begin their bid to ensure that they become the first team in Premiership history to avoid relegation after sitting bottom of the table on Christmas day.
Minute-by-minute:
6 - After a slow start, Hammers create the first chance of the game, as Schemmel combines well with Lomas on the right and flicks in a cross with the outside of his boot that Defoe heads over the bar from 10 yards out.
7 - Having sparked into life and lifted the tense Upton Park crowd, Hammers go close again, as Lomas' flick on drops to Pearce, who hooks his shot just wide of the target from the edge of the penalty area.
11 - Defoe 's slightly mis-hit shot on the turn from 12 yards out almost deceives Jaaskelainen, who only manages to parry the effort before gratefully pouncing on the ball at the second attempt as Pearce closes in.
17 - GOAL! Hammers get the vital opening breakthrough that everyone had been praying for, as Defoe's clever flick-on splits the Bolton defence and releases Ian Pearce, who takes the ball in his stride, cuts across Bergsson into the area and coolly slots under Jaaskelainen for his second goal in three games. West Ham United 1 Bolton Wanderers 0.
25 - Hammers get a lucky escape as Pedersen battles through a crowd of players in the area and turns well before firing in a left-foot shot that beats James but cannons off the post and bounces along the six yard box before being cleared by Carrick. Cole then picks up the long punt upfield and beats Frandsen before bursting into the box and seeing his low cross deflected away for a corner.
29 - Cole's flighted cross to the back post is nodded back into the danger area by Sinclair and met by Lomas, whose header clears the crossbar by a few yards.
31- Bolton come close again, as Djorkaeff squares a free-kick to Frandsen, who unleashes a blistering right-foot shot from 25 yards out that James beats out superbly before seeing Repka clear the rebound.
42 - After a cross from the right isn't dealt with, Okocha pounces to fire in a low shot that takes a deflection that flies up and over the diving James but thankfully just past the post for a corner.
Added time: 1 minute.
Half-time: West Ham United 1 Bolton Wanderers 0.
Second Half:
46 - Substitution for Bolton, Whitlow replaces N'Gotty.
51 - After James' long kick is only half-cleared by the Bolton defence, Sinclair goes close with a scissors kick from 25 yards out that dips just over the bar.
55 - Whitlow booked for foul on Schemmel.
56 - Substitution for Bolton, Ricketts replaces Djorkaeff.
56 - Carrick's free-kick goes through the crowd of players in the six yard box and drops for Defoe, whose low shot is cleared for a corner. From the resulting kick, the ball again falls for Defoe, this time closer in, but his toe poke is blocked by Jaaskelainen.
64 - Gardner's back-flick lets in Sinclair on the right hand side of the penalty area, but the Bolton midfielder gets back to put in a superbly timed tackle and concede a corner.
65 - GOAL. Bolton snatch a surprise equaliser that has an extremely strong suspicion of offside about it. Okocha controls with his back to goal just inside the area and flicks the ball over his head into the six-yard box, where Ricketts appears at least two yards ahead of the Hammers' backline and chests down before flicking past James. West Ham United 1 Bolton Wanderers 1.
76 - A typically mazy run from Cole on the right takes him past three opponents and into the penalty area, where he is blocked off by a defender who clearly doesn't play the ball, but referee Bennett amazingly waves play on.
79 - Lomas' long ball forward is flicked on by Pearce and reaches Defoe, who beats Barness and clips the ball past Jaaskelainen, but without enough power and Bergsson gets back to clear.
81 - Substitution for West Ham United, Hutchison replaces Pearce.
88 - Sinclair wastes a glorious chance to snatch a late winner, as Lomas' cross finds him unmarked in the six yard box. Somehow, he heads the effort wide of the post with only Jaaskelainen to beat.
Added time: 2 minutes.
Full time: West Ham United 1 Bolton Wanderers 1.