Lost Ber rune on ps5 offline

Wtf! I just found a Ber rune.. I changed the players 8 settings and saved changes to force that little pentagram autosave symbol in the bottom right corner, thinking that this would ensure that I would'nt lose the rune. I placed it in the shared stash tab. Exited the game and when I came back in the rune was gone! How can this even be a thing so long after the release of D2R?!

How do I avoid this from ever happening again? And when do I know for sure I won't lose an item?