UPDATE:

Seems I did a stupid thing last night. I think I inadvertently abandoned the quest while trying to exit the dungeon early due to maintenance starting. I believe I must have pressed J and hit abandon instead of U and hit abandon or vote abandon. I was very tired and the run was not going smooth, we would not have had time to finish. While this is my fault, of course, and I'll have to restart the Malice side-quest, it's worth noting that I have to confirm to throw worthless items away, or to go through a door to my house or FC house (and the default confirmation is "no"...why??), but there is no confirmation or warning for abandoning a quest you've worked weeks on. Live and learn. :/