I am having trouble retrieving the Gauldur amulet fragment from Geirmund's Hall after clearing it before I was aware of this quest. Now when I return the quest indicator points on the floor in boss' room, specifically on a patch of submerged dirt. The water is quite shallow and I am quite sure that there is nothing to pick up there.
To me it seems the quest has bugged as I killed the boss before embarking on this quest, or killed him while unaware of the quest and not picking the fragment up. How can I get around this? Is there a console command which can help me?