Oh well boy do I have several cases of that happening. Two most notorious ones, however. When I was a teen, I had a PS2, with loads of games and two memory cards. I'd keep most of my saves on one, and the bigger ones like Gran Turismo on the second card. I'd also often take the console everywhere with me if I was spending a day at someone else's house, and I was spending a lot of time at my grandma's at that time over school vacations. My little brother, who was then like 5 or 6, would go along with me, but do his own stuff while I played games on the upstairs TV.
One day, when I was playing Need for Speed Most Wanted, pretty close to the end of the game, he kept playing around by running across the room, and I kept telling him to stop. He didn't, and eventually his legs caught on my controller cable, and pulled the entire console down from the TV rack it was sitting on, about 4 feet off the ground. It was an old brick model, so somehow the console itself was fine, but it landed directly on top of the memory card and snapped it in half. Almost all of my savefiles, for many games I had finished or was still playing, were all gone. Immediate angry screaming, and repeated punching of the nearest furniture, but there was nothing to do about it. I set up the videogame again (and my brother NEVER ran around like that again) and it was still working, but I had trouble returning to some games later. To this day, I have never actually finished Most Wanted, despite playing it again several times.
Another, separate and much more recent event, I played a LOT of Dark Souls 3 since it released. Finished the game several times, and created 9 characters for invasions PVP at different level ranges, each one with a unique build focused on a different thing. Several hundred hours type deal. BUT, I never finished the DLCs, because the later areas ran like ass on my old laptop. So, when I finally built a proper gaming PC, I worked at backing up all my stuff that I needed to, and transfer it over. However, Souls games manual save backing up is... annoying and unclear. It's a simple folder with a bunch of numbers and not much else to identify it through. So, comes my surprise when I installed it again on my new PC, and I find out I accidentally saved a much older version of the file over the proper more recent backup. And that since then, I had already formatted the old laptop clean. No screaming this time, just feeling sad.
I've since tried starting a new character again, but playing through the early game areas for the umpteenth time is just not fun for me anymore, so I never got it going again. I'll probably sooner replay Dark Souls 1 than actually see out the end of the DLC on 3.
