[Dr Winston O Boogie jr]

It's up to the player to determine where the ball crossed the line. If other players disagree they can call an official who should settle the question. If it's simply he said, he said then the player's opinion will stand unless there are multiple players objecting. The officials also have the option of calling the television booth and having the head of officiating look at any video evidence.

If their fellow competitors made no objection then they probably agreed with Billy. It seems that the OP is the only one that saw it the other way. I'm not saying that he's wrong, it's just that everyone on the course seemed to be in agreement. It is possible that they were all wrong and simply missed it. Bad calls happen in golf just like in every other sport.