Was your inventory full when you talk to Bes?
Try to drop/cancel the quest and retake it, and make sure you have 1 empty space in the inventory to receive the third part.
....not sure what to make of that.
My inv. is never full, I make a pointof keeping it clear, so I autoran back to the town to drop/retake it, and opened my inv. on the way to check other stuff and there the last part was, just sitting there.
I definitely didn't have it before, I tried to fuse and it wouldn't let me...is that some kind of epic, epic item collection lag? o_O