i was sure this question had been asked before but a search (Callistratus site:longbowgames.com/forums) on bing (screw google) only turned up this. i dont think that will help as you seem to be saying u had him once and lost him.
the one i remembered had a lot of replies and a console command i'm sure. so it must have been another quest npc. the only thing i can suggest is search in your asset list to see if he's listed, if he is u can select him from there and give him new move orders. if hes not listed and u definitely had him before, you can email email@example.com if they havent already answered it on this thread.