The decision proved costly for Cooper as Matt McClure gave Wycombe's survival hopes a massive boost as he scored a header in the second half to take all three points.
Jack Barmby had earlier given play-off chasing Hartlepool the lead before the break but Wycombe came from behind thanks to second-half goals from Dean Morgan and McClure.
Cooper said: "The referee said there was contact but that it's a coming together.
"Who knows exactly what happened. He got bundled from behind and lost his footing.
"The defender's trying to get back and he can't get goal side of Luke. He's putting him under pressure from behind to try and avoid Luke from getting a shot off but he's bundled him over.
"It's a penalty and a red-card. We can't do anything about it because he hasn't given it. Why can he give decisions all over the pitch but not make the big ones? It baffles me but I can't do much about it.
"I've had a word with the referee to have a look because we believe we've been harshly treated.
"I know for a fact that if I went into the referee's office half an hour after the game that the answers would be ready so I'm not going to do that. I've done it twice this season and it becomes a pointless exercise."