TikTok follow

This guy followed my friend and she followed back. Btw us three went to class and I’d thought we’d in touch by following him. Literally a week passes and no follow back. He follows literally everyone we know but me. So I unfollowed because I looked like a fan lmao. Anyway what’s the logic behind this? Don’t really know how it works with the system but my acc has always been private but his is public. Maybe he didn’t get a notification?