[AnimalMuppet]

I was bringing up a new CPU board with the OS on a hard drive. It contained the only instance we had of the OS for that CPU board. And somehow I managed to delete the file that contained the OS kernel.

The board still booted, because the boot sector still pointed to the sector that the OS kernel file had been in, and the contents of those sectors hadn't changed. But the sectors were marked as unused on the disk, and could have been overwritten by any file write.

I booted for two days from that deleted file before I got to the point where I could re-create it.