The Chairboys boss believes that the dismissal had a bearing on the outcome of the game and hints that he could mount an appeal against it.
"It was not a sending off in my opinion, but mine doesn't count and the referee's does," PA quotes him as saying. "All of my players didn't think it was one and I've spoken to Neal Ardley and he said 'very harsh.
"It's hard to play with 10 men, especially for 70 minutes, but the boys did themselves proud and until the last five minutes when they had a few shots on goal, you could see we were equal to them.
"The red card did come at a crucial time and they scored within two or three minutes of that and then it was very hard to get things in place.
Ainsworth will now look over video footage of Lewis's challenge before deciding whether to challenge the red card.
"At half time we sorted it out and we nullified their threat and a few players turned my head," he added.
"I'll be without my skipper for three games - I know red cards have been rescinded in the past but I'll have to look at it on the video myself."
Luke Moore headed the only goal of the game during the League Two clash.