rulefan
Tour Winner
Regardless of any difficulty, in match play it it is for the player to make a decision and for the opponent to register a claim if he disagrees.Whilst the competitor is responsible for making the decision it would be very difficult if their opponent said they were not happy with the decision. In these circumstances I think you would have to proceed as if the ball was lost rather than being in the hazard.
The player is not obliged to do anything based on his opponent's view.