A woman is sitting in her hotel room when there is a knock at the door. She opened the door to see a man whom she had never seen before. He said "oh I'm sorry, I have made a mistake, I thought this was my room." He then went down the corridor and in the elevator. The woman went back into her room and phoned security. What made the woman so suspicious of the man?
But what if actually the man book a room for 2 people (with his friend) and decided to knock first before entering?
You do realise that this was my riddle at first, did you get it from me?