Who entered the wrong room?

During the summer vacation, Xiao Wang traveled to the seaside alone and stayed in a hotel by the sea.

Late that night, he vaguely heard someone knocking at the door, thinking it was a waiter. When he woke up, he was a stranger. As soon as the man entered the door, he shouted, "Hey, how do you sleep in my room?" Xiao Wang said, "Excuse me, this is my room 303. Are you going the wrong way? " The man looked around and said apologetically, "Sorry, I made a mistake. I thought it was my room 305? " He said that and hurried out. Just walked to the door, suddenly Xiao Wang shouted "Stop thief" and grabbed him from behind. Passengers and waiters in the same building heard the news, listened to Xiao Wang's analysis and immediately handed over the man to the public security organ. After interrogation, the man was indeed a thief.

Why did Xiao Wang insist that the stranger was a thief?

answer

Why did the thief knock when he entered the room?