So you met the guy three weeks ago, and he followed you around, but you’ve never actually spoken to each other, even when you were alone. Gee, that sounds awkward.
How can the guy even know if he likes you? What does he know about you? He might have been interested enough to follow you around for a few weeks, but if neither of you was brave enough even to say hello, I’m not surprised he gave up.
You’ve never talked. If you want any chance of getting to know someone, the silence needs to be broken. So if you think you like him, just say hi to the guy.