This is a somewhat hypothetical question based on something which happened to a friend of mine who does AirBNB in the Chicago area. He had a guest checkout with no problems, but then about three days later, the man was back at my friend’s house in the early evening, knocking loudly on the door, claiming he “forgot” something and needed to get back in the house. I think it was a basement apartment deal, with my friend living upstairs, and he knew there was nothing which had been left and suspected this was some type of attempt to get back on the property to possible to commit robbery. My friend didn’t open the door and the man eventually left. I don't know if a police report was filed.
So, my question is, what would one do if a checked out guest managed to somehow get back on the property, hours or even days after leaving, and then claimed that they had an emergency and needed to stay again. Would the best course be to call AirBNB? Or simply treat it like a straight up trespassing, breaking and entering situation, and dial 911. Opinions?