The incident happened after the goals had been scored when Paul Cairney appeared to be caught by Michael Nelson, but referee Bobby Madden booked the Hibs player for simulation instead of pointing to the spot.
Fenlon opted not to hit out at the match official, but the Hibernian manager admits the blunder is be costly as Cairney will serve a suspension after his latest caution.
"I haven't seen it so it is difficult to comment," Fenlon said. "But Paul said he caught him and some of the players who seen it on the televisions said it was a penalty.
"These things happen. I am not one to come in and criticise the referee but if he has got it wrong I am sure he will hold his hand up.
"Maybe I need to moan a little bit more and I might get a few more for us but some of them go for you, some of them don't.
"I am more disappointed with the yellow card because we will lose Paul through suspension and that is more disappointing than the actual decision."