More & more frequently the Vault 13 Canteen, (pre order DLC bonus), is not found in game. I've even loaded early game saves where I know it is & it's absent from those saves.

No, I didn't misplace it or sell it. That was my first guess so I started loading old saves all the way back to Doc What'sHisName's house & the item was missing from ALL old saves.I paid for this stupid item now I'm wondering where the hell it keeps disappearing to. I've had the item not load many times and then out of nowhere during gameplay I'll get the message:
"Items added to inventory:
Weathered 10 mm pistol
Vault 13 Canteen
(some random ammo)"

Once returned to inventory it reappears in old game saves also.

Early on it was a rare random occurrence but now it's almost constantly absent from my game.

I have no idea what triggers the absence or the reload of the items.

Any info much appreciated.