I suppose that depends on just how in touch you all were in the first place. Was this a boyfriend, a really good friend, or an associate you met out who you showed chemistry with?
It's possible that he really meant it. Until he moved and then it became out of sight, out of mind. Not even on purpose. It just is what it is for a lot of people. People move and their lives take over. They're busy or they are out meeting new people, etc. Who knows. Maybe he would be interested if you were around him, but you're not and the reality of the situation caught him by surprise and through natural attrition, you fell out of importance.
Or maybe the world will end in 2012. Who knows? But I will say this, if he hasn't contacted you, then if you can, just leave it alone. I know that's easier said than done because you really want to know what happened. But you may never know. You may never hear from him again. Or maybe when he comes back to your city he'll reach out to you and then you can ask him. Or you can ignore him.
The safe way to look at it just might be that he lost interest since that's the easiest to move on from. Sure you may want to know why but you have a built in default answer: he moved.
Let it go. Let it flow.
Do yourself a favour and heed BFFs advice. Never mind the whys and what the effs. In this day and age, there are a million different ways for him to reach out to you, so if he isn't....at best it means he thinks you're a great gal, but he's not up for the inherent seriousness of something long-distance. I tried to get together with a guy long distance; it took me a while to accept that it just wasn't gonna happen. God bless the guy; he tried to let me down gently over a couple of months:
"So, let's write to each other; i'm not so good on the phone."
"You shouldn't be so nice to strange guys."
"Why don't you go and live with your sister on the other side of the world?"
"I really want to see you again; I just hope you don't have any expectations."
"I'm not what you would call a romantic"
"Life's a bitch."
"I hope you still want to stay in touch once in while."
Never heard from him again after that one!