I think, as has already been said, that you should talk to him about his disappearing acts, and find out once and for all, what the heck is up with him. It sounds like there could really be something there, at least, ... for you, although I dunno about him, ... I've known some guys who act like that... it's all buddybuddy, friendly-flirt, crap like that... I think I've had it myself from a girl actually, some yonks ago. Just get it out in the open, the next time he swings around for some feelgood, and there you'll get your answer.

(expect the whole "Oh? I only meant it as a friend." speech; I got the same and didn't expect it, and so it hurt a lot more, so just be prepared - disconnect yourself from him a bit, if you can)

The reason I think you need to be careful, is because he may just be going to you for some pick-me-up (hence my sarcastic "feelgood") because he knows you like him, and wants to have that feeling of being wanted, at your expense. It's really nice to feel wanted, and that's OK, but to go to the lengths he's gone, if that's what he's playing at, then that's pretty sick, IMO.