I had one important project (I don‘t remember anymore which one it was), so I put it on THREE 3,5‘‘ disks, one after each other.
All three were unreadable by the time I arrived. I was devastated.
(note I had heard stories about rotating current brakes ruining disks so I took care not to go by rail, must have been something else)
It was around midnight, I was done and hit save. I had an external monitor, and for no particular reason, decided to move it around during the save. It was big and heavy, and while moving it I accidentally hit the power switch of the PC.
Powering off the machine during disk write destroyed everything. I couldn't believe it, I stared at the machine for a while.
Then I spent the rest of the night recreating the document from memory, while making frequent copies on different disks.
It was a horrible moment that I remember vividly, but it taught me a valuable lesson. I never again lost any file for lack of appropriate backup.
Putting the disks back in the original drive and they probably would have been readable.