He never mentions his girlfriend?

So this sweet shy guy I met about three months ago, we became really fast friends and were talking all the time about everything for a couple weeks and I was sure he was into me. We became facebook friends and it said "in a relationship with so and so" and I was crushed. But we continued friendship with me still liking him, and it's been months and we've become really close and still no mention of the girlfriend. I've deduced through facebook it's a long distance thing btw. And looking through pics on fb I saw that they went to prom together in high school, but he was telling me a story today abd said "the girl I went to prom with." what is up with this guy????