The midfielder was dismissed in the second half by referee Michael Oliver when he lashed out at an opponent.
The on-loan Robbie Keane then scored late on to seal the win for Alex McLeish's side.
"I'm told that it's a sending off," McCarthy told BBC Sport. "He admitted himself he kicked out so if he did then it's stupid and it's cost us."
The defeat has seen Wolves slump to 19th in the Premier League table.