Hello! Like suggested in the FAQ, i post the bug to help:
It is happening each time to me (Win 10 x64 pro), and it is easy to reproduce:
Set a pile of items (the same ones obviously, if not it doesn't "stack") on the floor... (if you pick it up after wihtout "save & quitting", no problem... there are here with the right numbers for the stack)... but save & quit... and even without exiting the game (on the menu), load the current game and you will see the item on the floor but there is only "one"! the stack is gone! (the first time i lost 5 artifact! :-O OMG! lol)
I tested with artifacts, wood... same thing; i think it is the case for every items in the game. I think the autosave doesn't include the number of items on the floor for the stack. (may be easy to resolve! B-]
Glad to Help! =^^=