"Titans' Treasure" doesn't spawn

"Titans' Treasure" objective in The Titan Grotto doesn't seem to appear. I've explored the whole area and killed most monsters (except the boss), but there's nothing.
There was a checkpoint next to a titan stabbed with a sword, but there was nothing there to interact with.
In my previous run through the area, I killed something that dropped me an uncut spirit gem and I thought that might've been the objective somehow, but the icon on the world map is still highlighted so it didn't count as completion.

Same here.