Why won't he approach me again?

I can't for sure tell you this is right, but it sounds like you almost scared him some. If he had his friends at a distance, you made him nervous, and he didn't want to be alone when he asked you on a date. The smile probably means he was trying to blow off his rejection. He probably wont ask you again because he's intimidated by you. He probably was into you and may still be a little bit, but He may be a little afraid to approach you again.