I didn't lose ALL my code but in 2006 about 1 week after presenting my RPG in the "help wanted" forum here on GameDev.net, my whole computer crashed and I lost most of my campaign editor and a lot of code improvement. I had a >1 year old backup but it was on a diskette, which should give you an idea of how much I lost. :(

I feel sorry for the people who answered my post and actually sent me stuff, I was so upset that I never answered emails after that. (I guess I'm a bit of an ass when I lose work, heh.)

Now, I host my project on a Git repository on Visual Studio Online with a backup on OneDrive and Google Drive so unless the Yellowstone supervolcano explodes and engulfs Sillicon Valley under a kilometer of hot magma, I should be safe. :)

It happens even to publishers.

I used to work for a studio that was doing handheld games for Atari (Infogrames Atari, not Atari Atari). Some day, they decided to bundle together two GBA games into one cartridge, one that our studio had done recently, and some older game that had been developed elsewhere. We asked for the source of that other game, and of course, they were thoroughly unable to locate them. All we could have was a binary image of the game's rom.

Since we had to add a launcher to select which of the two game to launch, we ended up having to place the older game at the beginning of the rom (since without the sources we couldn't relocate it to a different address), overwrite its first instruction with a jump to start the launcher, and jump back there if the user chose to launch that game. Our own game for which we still had the source was recompiled to run from whichever address we ended up putting it at.

A little over ten years ago, my original iMac's PSU/monitor driver board (STUPID design!) died. I didn't have the money to replace the computer, so I rigged a ATX power supply and connected the motherboard to a VGA monitor. I had everything out of the case with the motherboard lying on my desk. Everything was great, until someone broke in and stole the external hard drive that they mistook for the computer. They left the motherboard and PSU, but stole the hard drive and monitor. Everything I had worked on for more than a decade was on that drive!

In the past, I did some tinkering with programmable cartridges for the Nintendo DS. I made a working port of Angband which I ended liking and playing for quite a number of few hours. I have no idea where the source code is and I've sold the Nintendo DS and all the cartridges since.