Knock Knock - Detective Riddle

Aalia is on a blissful vacation after helping Detective Mehul catch bad guys. She 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, I'm sorry. I have made a mistake. I thought this was my room. He then went down the corridor and into the elevator. Aalia went back into her room and called detective Mehul to arrest him. What made Aalia so suspicious of the man?

If it was his room, he wouldn't have knocked. If it was his room, he wouldn't have knocked.