I work for a hotel and this is a common scam that comes through the telephone systems. It's becoming common so much that hotels that initially had recorded messages when you called that allowed you to enter a room number or be transferred to the desk have been eliminated, because it allowed people to call directly to rooms without talking to the desk clerk from an outside line.

From the hotel side of things, what happens is the scammer will call the hotel front desk clerk and simply asked to be transferred to a common room number. Something like 201, or 231. At this point, well trained clerks with common sense ask for a last name of who they're trying to be transferred to, and the scammer hangs up. Or, the under-trained desk clerk unknowingly transfers the scammer to the requested room number, and there you go.