lets face it, eye contact is #1 impt thing when it comes to liking someone.
now for guys, why would you look at a girl you rejected, didn't like back, didn't take it further, not interested in?
Most Helpful Guy
I answered a similar question before, this is somewhat what I said:
He checks you out because he thinks you're pretty, beautiful or cute in some way or another. Since he rejected you it is probably mostly a physical thing. He could be attracted to aspects of your physical appearance or mannerisms or both. Just like you can stop listening to a beautiful song or removing your eyes from a beautiful piece of art, this guy can't remove his eyes from you; unless you look back at him, of course.
In your case, did he check you out before he rejected you? if so, what I said, might be the case. Otherwise it could be something more complex, like him realizing that you attract him after you told him that you like him. If so, though, that doesn't mean that he wants or is ready for a relationship with you.2