Is there any truth to the statement "Absence makes your heart grow fonder"?

I ask this because I have this friend, who I met in '08 at work. In summer '09 I found out he liked me. I didn't really like him in that way though, and rejected him. We have only hung out a handful of times since he quit, since we live in separate cities and both got busy (me with college, him with work). We talk quite frequently though, and I consider him a good friend. However, lately I've been feeling like I might start to have feelings for him. I don't know if this is just because I haven't seen him in a while and I miss him, or if my feelings go beyond that. How do I figure out which is which? We're making plans to get together in a few weeks, and if it turns out I do have feelings for him, I want to tell him, but I don't want to say anything unless I know for sure. How do I tell if it's just me missing him or if I've actually developed feelings for him?