Comment by Schnitz

The lost+found folder saved our backs once way back when. We had a 1TB NAS running Linux, an enormous amount of storage back then. It was shut down unexpectedly and disorderly and ran a multi hour fsck upon reboot. The volume must have had a shot root inode, as after the machine booted and mounted the volume it was empty. All directories were luckily under lost+found with all their contents.