Referee Alan Muir had no hesitation pointing to the spot after Paul Hanlon had tripped Gary Mackay-Steven late in the second half.
Johnny Russell converted the kick but television replays suggest that the foul had taken place outside the box.
Asked about the decision McNamara said: "I've not seen it again.
"I thought there was a foul on Johnny before it that we didn't get.
"Some people are saying it was outside the box but I thought we deserved at least a point for the second-half performance."