Wolves boss Gary O'Neil says elite referees manager Jon Moss told him he "could not believe" his side was not given a penalty at Manchester United.
The home side won
1-0 at Old Trafford thanks to Raphael Varane's header.
O'Neil was furious his team did not get a late penalty when United keeper Andre Onana crashed into Sasa Kalajdzic and failed to make contact with the ball.
"Jon Moss said it was a blatant penalty and should have been given - fair play to him, he apologised," said O'Neil.
"I have spent a lot of time with him today to understand the new guidelines, trying not to get myself booked in the first game, which I have failed in.
"But fair play to Jon for coming out and saying it was a clear and obvious error - he couldn't believe the on-field referee didn't give it and can't believe VAR [video assistant referee] didn't intervene.
"It probably made me feel worse, actually, because you know you are right. I feel worse about leaving with nothing. Live, I was told they didn't think it was a clear and obvious error."
Moss, who was appointed general manager of England's elite referees within Professional Game Match Officials Limited (PGMOL) in April, sought out O'Neil between his broadcast and written media obligations.
It is understood PGMOL chief Howard Webb also contacted Wolves officials after the game to apologise for the mistake.