It was a classy thing to do. He didn’t have to give the ball back. The golf museum has a new addition and this lucky guy probably has free tickets to next years Masters.
I fully agree with you..the ball was voluntarily given to the fan without expectation for return. Giving it back was a gracious act by a true golf lover.
Any good golfer will agree that golf is one of the last honest games out there. Golfers will tell on themselves when they have violated the rules, all the while when no one else saw them do it.
Consider other professional sports, like football, when a player, such as a receiver, blows a route and looks towards the ref for an interference or holding call that never happened...
The guy had no legal obligation to return the ball...he had a moral and ethical obligation...I don't know the details but I imagine the reward was offered, yet not demanded - at least that's what I am going to believe.