Leigh Griffiths' 40-yard free-kick just under 20 minutes from time in the 0-0 draw at Easter Road hit the underside of the bar and crossed the line before bouncing out with the match officials missing the fact it should have been awarded a goal.
Fenlon remained calm at the post-match press conference but said goal-line technology is a must in today's game.
"I'm disappointed for the players to be honest," Fenlon said told Sky Sports. "I've watched the replays and it's not even close to being on the line; it's a good yard, it's almost touched the back of the net.
"Maybe the officials should be out answering questions.
"If you throw that in with the Dundee United decision a couple of weeks ago where we've had a penalty given against us, it's four big points that's cost us.
"I told (the referee) it was in. He said if he's not sure he can't give it. It's his decision but it's clearly well over the line."
Regarding goal-line technology, Fenlon added: "I think in general that's the one area I'd like to see change.
"The fact that it's a goal and it decides the game, it's vitally important to get it up and running."