Have no clue if it’s in one of these 71 responses but…
If you have a weapon “in hand” when you pick up one of those large treasure items (the kind that you visually carry). You will DELETE the weapon you had.
…lost my one Star Metal Hammer after picking up a treasure that used the Treasure Coffer’s ‘treasure chest’ asset. Wasn’t in my inventory, wasn’t on the ground, wasn’t in my Thrall’s inventory, wasn’t present after relogging. It was just gone.