How do I know if the mouse left my room? Do they just stay somewhere quietly or move?

Houses have their own creeks and noises. Most likely the mouse is gone if there is nothing to eat. Maybe ask if you can borrow a cat for awhile. I have loaned mine out. You know a mouse is pretty harmless don't you. But I understand, they are a nusance. If you have a store bought sticky trap and haven't caught it then its gone. Sleep better now.