Fox was only sin-binned fo a butt on Cammy Mather and appeared to get off without any punishment for a further such offence in the second half.
While Eric Darriere, the French match referee, was on the other side of a ruck, one of his touch judges picked up what television viewers clearly saw as Fox appeared to butt Cammy Mather just 12 minutes into the match.
Hugh Campbell, Glasgow's coach, was incensed by the failure to take further action, particularly taking into account the second offence.
"We are surprised at the leniency of the referee," he told today's Herald. "It should have been a straight red, so a citing is a definite possibility. It happened on the blind side and possibly the fact that the referee did not see it himself may have influenced his decision."
Like the referee, Jon Petrie, Glasgow's captain, did not see the incident himself, but he agreed with his coach's view.
"Obviously if it does prove to be a butt, it's a red card offence and he should have been straight off the field," said the skipper. "It might have made a difference against 14 men, but there are other things that lost us the match."