Two goals from impressive Hammers striker Richard Garcia, the winner from the penalty spot, did the trick for the visitors after Michael Malcolm bagged his first goal for the reserves to level the scores.
Boss Colin reflected: "Overall it was a tight game. Games like that are often decided by mistakes and we contributed to their goals more than they contributed to ours. I thought ours was a decent move and well taken.
"There wasn't much between the teams. I think they had a bit more power up front, the boy up front looked a decent player, but we controlled the majority of the second half.
"Even in the first half, it was a very good strike for their goal and then mistakes led to us giving away a penalty when we were pushing on. I don't think Sully had much to do, perhaps we didn't work their keeper too much either, but there were few chances and little in it."
Colin Calderwood conceded that mistakes cost us dear in a tight reserve encounter against West Ham on Tuesday night.