I'm having the same problem here too, on Steam/PC
Received the quest before even reaching to the point of choosing Treviso or Minrathous, did the quest, it was just a single dialogue scene (which was weird for me since the others were longer quests, walking to the city, etc), so I even thought the quest shouldn't have ended there, but simply saw that the quest disappeared. It wasn't on my log of completed or anywhere, as if it didn't exist.
Tried to reload the game and did again, same thing happened!
I'm afraid of keep going because if this is a bug and also his romance lock is a bug, I'd prefer to save Minrathous and still romance him, since I made a Shadow Dragon. If not, I'm just afraid to keep playing and not be able to do his romance at all. :(
