Yes, an intriguing question. If you are talking of a social round, why should he not be delighted that he had a hole in one off the red tee? Possibly more creditable than my one and only (so far) hole in one, which was in a bounce game and came about as the result of a most embarrassing mishit off the blade which never got more than 10 cms off the ground, pitched halfway to the hole and somehow rolled the rest of the way to the green and into the hole.
But I digress. In terms of a game played by the Rules, this would not be a hole in one in stroke play because the player played from the wrong teeing ground which means a 2 stroke penalty and the requirement to play again from the correct teeing ground. If he does not go back and put the matter right he is disqualified. For handicapping purposes, is that one of the instances in the USGA system where you can miss out a hole and put in an estimated score? In a Qualifying Round in the UK, it would be recorded for handicapping as a nil return and be counted as a nett double bogey. If he did go back to the correct teeing ground to play from the right place, he would be playing his 3rd shot.
In match play, he could get away with this being a hole in one, provided his opponent did not require him to replay the stroke from the correct teeing ground. If he was required to play again, he would just have to hole his tee shot from the correct place to get a hole in one that way, there being no penalty involved.
The reference is Rule 11-4