This is one of those glitches where he is in a faction of his own, and basically completely MIA from the map. I've run into situations like that. Have someone sitting in Han but I can't find him anywhere, and he just randomly declares war on me, and then never does anything. Not sure what the hell is going on with it, but I need him to leave so that Han can be defeated finally.

Basically for your situation, you've just got to keep your eyes open as you play the game, looking at each Deserter you come by. Since it's 100 days ago though, I'd put money on the idea that he isn't with the deserters anymore, and is most likely captured by someone else by now, or somewhere randomly on the map just standing there.