City lost 2-1 at Loftus Road on Boxing Day but the result may have been different had referee David Phillips taken a different view on two penalty claims.
"My only gripe is that the referee looked at his linesman with a question mark on his face, and the linesman looked back with the same question mark and so they just played on," Johnson said.
"I could say we were robbed but we have to do more as a team to compete in the top half of this division."