Hughes made mention along time back that he had been in the military at one point. I remember because he said something about the Navy so with me having served in the Army, we had kind of a friendly, "patriotic" kind of rivalry. I don't know if he's still active duty (maybe reserves) but if he is, he may have deployed somewhere.
The other, more likely answer is that he comes and goes a lot in this game. Almost feels like he gets burned out, stops playing for a while, then starts back when his batteries are charged back up. This isn't the first time he's taken a hiatus from the game, so I wouldn't worry too much just yet.