rulie
Head Pro
Well, he did proceed correctly under the unfortunate circumstances.As an example to help clarify the question. The player was the first to hit his tee shot. It went onto the adjacent fairway and was clearly at rest. The rest of the group then teed off and walked forward. On the other fairway a group was playing their shots. We didn't even go to look for the our playing partners ball as it was so obvious where it was.
When he got there the ball had gone. He challenged the other group to ask if they had played the wrong ball - they denied it. He also asked if they had picked it up in error assuming it was lost and again they denied it.
The ball was very clearly marked with a thick blue wavy line so very difficult to argue it was a case of mistaken identity.
The nett effect was he had to go back to the tee under penalty but it also ruined an enjoyable round for him.
For the avoidance of doubt, if the ball had gone onto another fairway but was not clearly visible I have no issue with a S&D penalty.