Why does it hurt?

I consider myself a fairly rational person. But it's funny (not ha ha funny but more odd funny) that some things can really get to me, despite what I'm sure is a rational explanation. So I have this friend, and I'm fairly sure that they won't read this, but if they do, please don't take this the wrong way, this is in my head and is not an accurate representation of you. Anyway, this friend, I'm not sure how to define our relationship because I've never had a friendship like this before. For some reason I feel compelled to befriend this person, and they just might hate it. Perhaps they don't want anything at all to do with me and are humoring me, praying daily that I would just leave them the hell alone. Perhaps, but I don't think so based on a lot of other things I won't share. This person doesn't get out much, or at least they say they don't. Basically because of a lack of time and a general resistance to social situations. Again, so they say. However, this is where the existence of an online social network can be problematic. See, other people can post pictures of you that show up on your friends pages even if the person who posted the picture is not your friend. So, on occasion, I get photos of my friend, hanging out with other people and seemingly having a good time. Except they won't hang out with me. And I don't know why. And this hurts. But, LOGICALLY, it shouldn't. There are a lot of people who like me, a lot of people who want me around, a lot of people who are willing to go to lunch or a movie or to the park. I'd even risk saying that most people who I know would be more than happy to hang out with me if I called them and asked. So why does it bug me so much that this person, this ONE person, doesn't want to? Or can't find time to. I've always thought that if someone really wants to be around you, they'll make time. Maybe that isn't a correct thing to believe.