I use a password-manager where i create 100+ chars passwords. When i wanted to back it up onto external drive, i had to close it first, and imo i saved the latest changes in it, i.e. new passwords for my new wallets.
But nope, they where gone ! !
Had to use the toilet immediately.

I bet that's Keepass. By default that thing does NOT automatically save your change/additions when you exit, unless you manually save or you change that setting in the options. I lost a few email accounts thanks to that feature.