When playing and putting iteams in a shulker box and then picking up said shulker box, I have gone through a nether portal from the nether to overworld and overworld to the nether and when my game crashes it loads the quick save. But for some reason, the shulker box I had been interacting with is not in my inventory, an ender chest, or where I left it in the world. And had been deleted from my world entirely it has happened at least two times