Well... it's the CM you pick up from the Mooks with the fake AD. Unless you've really been shuffling around. I know you can, but have no reason to, put the CM back on the holder. Perhaps you might have put the real one down by mistake. I'd look there. It wouldn't be with any of the NPC's as none I have run into would even take it.
Assuming, of course, that you DID get it in the first place - it's really hard to get rid of - you can't drop it or give it away. Do a 'by type' sort of your inventory.. the triangle, box and circle button -- it will go to near the bottom. Also check each of your party members personal inventories.
Hope this helps.