Heskey was incensed at being denied a free-kick after being on the receiving end of a challenge from Wigan defender Antolin Alcaraz. He made contact with the Cheshire official but escaped with a yellow card.
However, McAllister substituted Heskey at half-time "to make sure we finished the game with 11 men".
McAllister said: "I'm not skipping this issue. I'm going downstairs to watch it. I've not seen it.
"But if Emile did barge into the referee, he is obviously lucky. But it is very uncharacteristic of Emile.
"He was annoyed he wasn't getting protection from the referee. With a couple of balls he had won, the centre-backs came into the back of him.
"He was looking for a bit of help from the referee, he didn't get it but it was an over-the-top reaction.
"Knowing him the way I do, someone I admire, a good friend, someone I've played with, that was just not Emile."
McAllister added: "The decision to make a change at half-time was purely for the team. We had to make sure we finished the game with 11 men.
"I didn't think about taking him off straight away. I caught his eye and felt he was going to be in control until half-time and that was enough for me.
"I've seen him angry before but the previous time was for a horrible reason in Kiev with Liverpool in a Champions League match which he had every right to react.
"This was not the same sort of abuse he got that night."
When asked if Heskey will be disciplined, McAllister said: "He won't be disciplined by me. I know he is not happy with his reaction.
"I saw him before I came back onto the pitch for the second half and he had calmed down.
"Did he stay to watch rest of game? I am unsure. I've not seen him since."