From the Orlando ABC Affiliate Local News WFTV
Since June 2010, police have gotten reports of Price [the thief] re-checking into hotel rooms. He would apparently watch a guest leave then go into the room and claim he’s that person. Once in the room, police told WFTV Price would call the front desk and say he wanted to extend the stay, sometimes by 10 days.
On my last vacation I was told by the staff at the hotel front desk that I could just leave my key card in the room and call them to let them know I checked out. Based on what happened here, it seems that it's better to hand the front desk staff the key and ask for a receipt. Perhaps people were just leaving their key in the room, and this guy was able to walk by them as they left the room and prevent the door from locking so he could get into the room.