Well he was honest in telling you that he is in recovery and actually didn't want you to know.
Kind of honesty a bit late, but maybe he didn't feel you were at a point (previous to your visit) where he needed to share that with you, which is his choice, of course.
The flirting and whatnot might have seemed very harmless to him long distance but became a bit more real when you visited and perhaps he realized he's not ready for a relationship.
It's kind of impossible to say? You know him best. Is he generally honest and reliable. When he says he is going to do something, does he do it? Actions, not words.
The distance now may be him realizing this has gone too far for him to be comfortable with?
Again, guessing based on what you have shared.