Wycombe boss Gary Waddock blasted referee Keith Stroud after he awarded the penalty which Brentford converted to win 1-0.
The Chairboys now sit just two places above the League One drop zone following their defeat at home to the Bees on Saturday.
On the penalty decision, Waddock said: "Do you want me to smile or laugh about it? I think the only person in the ground who saw the penalty was the one who gave it.
"I've just seen it played back four or five times and it was an interesting decision.
"We'll be stewing about it tonight (Saturday), tomorrow and Monday. It's frustrating when decisions like that go against you. If it was a stone wall you'd hold your hands up."