Mirage not clearing(Probably resolved; mods can delete)

I just wiped the mud flats mirage with my second character, killed everything inside, but the mission isn’t completing. I tried talking to the ghost woman and she didn’t give me an option for finishing it, so I restarted the game and now she doesn’t even show up, just the portal.

EDIT: I'm thinking I picked up the chest by accident and didn't notice, although I'm usually pretty sharp. Seems like the simplest explanation. Mods can delete.