Stevenson's reckless first-half lunge on Hibs captain McPake could have changed the game had he been dismissed, but referee Willie Collum did not even book the Hearts midfielder.
Fenlon said: "I've just watched it. It's a shocking tackle. He had a look first before he left the ground. We're disappointed with that. He has a bad gash, James. There could have been a bit of damage there, but he's not too bad.
"But you can't be critical of the referee. I thought the referee reffed the game very well tonight."
Stevenson could be retrospectively punished by Scottish FA compliance officer Vincent Lunny for the tackle. Had he been cautioned no action could be taken.
Hibs defender Ryan McGivern said: "It was a disgusting tackle. It was a red-card tackle.
During the Dundee derby, Collum let a similar incident go before awarding a penalty and McGlynn felt his side should have had a spot-kick.
McGlynn said: "I'm not suggesting he played advantage, but I thought it was a penalty."
Since Hearts won May's Scottish Cup final 5-1, Hibs have drawn two league encounters and claimed a semblance of revenge in the cup by dumping out the holders in a fourth-round clash at Easter Road in December.