I got caught by this one. I searched and there have been others with this issue.
I have two idols... one pickpocketed and one from the Kiss quest.
The non-stolen one disappeared from inventory and I have confirmed this from loading game saves. This happened in Wrecker's cave.
A couple of things that happened between the saves:
1. Character died and idol turned ashen (however, game was never saved with ashen idol).
2. Idol was moved to another character who was in a separate area from the original person with the idol. (Wrecker's cave has characters separated for awhile, but inventory can me moved between characters).
The idol is not in any character's inventory, not in a backpack, not in a bag, and nowhere in the caves. It completely disappeared.
