so I assumed all your stash's were linked ( first time posting not really sure where to post about massive bugs this is on PC don't know for consoles) please don't read if you're not far in the game may have a few spoilers but ill try and keep story out as much as possible, so you start with your apartment stash , when you do a questline with Panam you get another stash place after a bit, i thought cool these must be linked (not really checking) i put all my iconic weapons in the stash unit...

Lost weapons due to stash bug?