I don't think you were anything other than a friend. A good friend at that and the kind of friend he was happy to have and probably misses. Here's the problem, he has a girlfriend now, and naturally, once we start dating, some of our friendships take a hit, perhaps unfairly. We start spending all of our time with them and are never available.
Our male friends don't take it personal because they know the deal. Our female friends tend to take it personal and get upset that we chose somebody over them.
Here's the other thing, female best friends are always the first to go because very few woman genuinely trust any other woman who's been that close to her man. For some reason, all women assume that every other woman wants their man despite all evidence to the contrary. Women don't trust other women either. So while he's not doing it on purpose, I'm sure he's just dating a woman who hasn't met you and isn't fully comfortable with the relationship you had. It's retarded and shouldn't be that way, but it is.
And it's normal.
It's just what happens when men and women have opposite sex best friends.
But don't take it so personal...I'm sure ALL of his friends are missing him too.