We had the same thing happen at Beach Club a few weeks ago. We had all tucked our shoes together neatly under a table by the pool at Stormalong Bay. When we came back after a dip for an hour, my daughter's Crocs sandals had been swiped. We reported it to staff (and Lost and Found later), but we had no luck. I could see if they were more in a walk area that someone could have possibly mistaken them as their own but not the way we had them lined up deeply under the table. ODD. (Lost and Found closed our case the other day with no success.)
Now I see that it isn't completely unheard of for it to happen. While we were at SB, I was surprised how many people left their purses, wallets, and cellphones just sitting out. I didn't think used shoes would be of interest to anyone.