Substitute Scott McDonald eventually opened the scoring for the dominant Hoops in the 79th minute with a close-range header but Lee McCulloch levelled two minutes later to keep the Ibrox side seven points clear at the top of the Scottish Premier League table.
Fortune, signed from French club Nancy in the summer, revealed his frustration at Conroy's controversial decision.
"I jumped and never touched the keeper, only the ball," he told celticfc.net.
"My first impression was that I had scored because the referee ran to the centre and then I saw him run back towards the goals, so I didn't understand.
"At first I thought the goal was offside, but then the referee told me it was for a foul.
"Sometimes the referee makes mistakes but that's just football.
"For about five seconds I was really upset, but then I just kept on playing.
"I think everyone that plays for Celtic and Rangers wants to score in the derby, particularly if you are a striker.
"This is my first year here so people will think I should score.
"I did - but then the referee made his decision.
"But I think the fans saw that I gave my best for them and there are a lot of games left so I will do my best to score in them."