Guy doesn't think I like him. Lost interest?

This shy guy didn't think I liked him because I guess he thought I wasn't interested in him (I never rejected him though) now he Doesn't show up where I used to see him, he didn't look at me even he was in the area, and he passed right in front me and kept his head down and didn't say hi.

How can I get his interest back when I finally do see him?

How do I know if I still have a chance?
Guy doesn't think I like him. Lost interest?
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