PC: Aracknar Blackgem
Upon unequiping my axe, it disappeared from my inventory and then reappeared a moment later. I was then able to equip my axe again. While holding it it would disappear then reappear. Strangely enough, other PCs had seen my axe on the ground while from my point of view and character sheet, I was holding it.
10 minutes later, randomly my axe disappeared for good.
Do you have your inventory absolutely full?
My inventory is close to it, its a mess.