Trailing Southend United 2-0 heading into the final ten minutes, the U’s appeared to have got a lifeline after a moment of magic from Cristian Montano.
The substitute jinked past three challenges before being brought down just inside the area, but referee Lee Collins instead awarded a goal kick.
Wilder said even Southend boss Paul Sturrock thought it was a spot-kick, which could have given United a way back into a game crucial to the club’s hopes of reaching the play-offs.
The United manager considered requesting the assessor’s report this week, but the experience of similar moves in the past made him think twice.
He said: “I’ve put three reports in this season about the standard of refereeing and every time I’ve done it the assessor has 100 per cent backed the referee’s decision.
“I could have done loads more reports but I only do it when I absolutely think it’s certain in our point of view.
“I just think it’s a complete sham and I’m possibly not going to waste my time on it.
“I had Paul Sturrock coming into me after the game saying their lad held his hand up and said he couldn’t believe we didn’t get the decision, especially here with all the support.”
The defeat left United as long shots to reach the npower League Two play-offs with only 90 minutes of the season remaining.
To claim seventh position this Saturday, they must win at Port Vale and rely on Aldershot winning at Crewe Alexandra.
Despite going six games without a win, Wilder did not believe his players would have a problem dusting themselves down for one final effort.
He said: “They’re professional footballers, they’ve got to take it on the chin.
“It’s not a disgraceful situation that we’re in, it’s just that we’ve not been good enough over the last four or five games to get the wins to match the performances.”
OXFORD United Reserves complete their league campaign this evening with a home game against Stevenage at Didcot Town’s Loop Meadow (7) which will be the club’s final outing in the Tote-sport.com Combination.
The U’s have withdrawn from the competition for next season and will instead arrange friendlies where needed.
FORMER Oxford United manager Brian Horton has left Macclesfield after failing to save them from relegation from League Two.