We did this once. We had just checked into our hotel, jet-lagged after about fifteen hours of travel. We showered and changed and had a quick bite in the restaurant downstairs, as it was about 3:00 pm, and dinnertime was hours away. We charged it to the room, signed for it, and then went out for a bit. When we got back to the hotel room that night, I looked at the door to the room and got this sinking feeling that I had given the wrong room number when I had signed the bill for our lunch that afternoon. I called the front desk to find out, and indeed, I had transposed two of the numbers. It was no big deal, as the hotel cross-references room numbers with names, so they would have charged it to us in any event, but I felt just awful about it.