Hammers boss Glenn Roeder is particularly annoyed about the decision - especially considering the side put in such a great performance against a very good Arsenal side.
"I don't think it was a goal, I know it was a goal," Roeder said. "You can clearly see the ball was over the line. If it had gone in, they'd have been more edgy and nervous.
"Right up until half-time the linesman remained adamant that it wasn't a goal. It was an honest mistake, but it was also a bad error.It's a linesman's job to spot these things. I just hope he holds his hand up and admits he got it wrong."
And Glenn reckons it could be the crucial decision that makes Arsenal champions, instead of either Liverpool or Manchester United. In such high profile and important games as these, decisions like this can prove costly. But if they make an error, they are not punished it would seem - another thing that vexes the Irons' manager.
"Decisions like that win championships. Had we taken the lead and gone in at half-time in front they might have become a bit nervous, but it wasn't to be.
"We're accountable as managers and players, and so should the officials be. They shouldn't just be allowed to scurry off into the night."
Despite the dodgy call by the assistant referee, Glenn was mainly pleased with the Hammers performance in the game, and particularly the lads' workrate.
"We've got to come out of the game with credit. I thought we worked very hard. We had a specific gameplan and almost pulled it off."