Yesterday I had the pleasure at the Historic Sheraton Gunter hotel of being checked into a room that was already occupied. This only happened to me one other time, at the Hilton Miami Airport hotel in 2002.
The check-in process was uneventful, and I was upgraded to a room on the Starwood Preferred Guest (SPG) floor. I went up the elevator to my room on the 11th floor. When I got to my room, there was a do-no-disturb sign on the door. I thought this was a big odd, but proceeded forward nevertheless. I swiped my key, opened the door, and walked in.
There was a suitcase on the floor, with clothes strewn all about the floor. There were toiletries unloaded in the bathroom. I am very happy and lucky that the occupant was not there at the time. I immediately left the room, and went back to the front desk to let them know of their error and to be checked into another room. They immediatley reaccomodated me at another room on the same floor, this one without an incumbent desk.
When the front desk was reaccommodating me, they called in for someone on their maintenance team to go into the supposed-to-be-vacant room and determine the name of the occupant based on something on the luggage. I found this rather interesting and strange but I do not know what came of it.