Mined two inventories worth of basalt, most was put it in a chest in the nether and more was still in my inventory when I logged out. When I loaded in the next day all of the basalt had disappeared from the chest and my inventory. All of the basalt I had mined was still missing from the world.

I am not sure, but I believe this happened between updating from 1.16.0.58 to 1.16.0.59