I've also had this happen, but in Act 2 after completing the Thaniel questline fully. Still waiting for a reappearance. In your case, I would double check last light inn by that one sleep cursed guy's bedside. If he's not there, maybe he's already by the portal spot. If he's not there either, well... Let me know if you ever find him...
I lost mine somewhere after attacking Ketheric, someone said he's supposed to be findable at Moonrise Towers after the quest there, but I reloaded and he was already gone by that point. Maybe my Durge was sleep walking again lol
