I have had "ghost stays" appear on my account. Marriott Amsterdam and Marriott Circular Quay have been the cases.

But more interesting, I once got a mail from an ambassador confirming the use of my SNAs for a booking. I was not ambassador at the time. Seems there was a US based CPH-FLYER ambassador, and somehow the ambassador agent chose the wrong account when using the SNAs. In the email reply that went to me, I could see that the name was the same as mine, and I could see the request to assign the some SNAs to a booking that was not mine. Eventually my SNAs were restored