The great thing about modern light boards is that they have non-volatile memory; turn the board off, and your show will still be in its memory next time you turn the board on. Unfortunately, this doesn’t protect your data from other humans.
“That’s why you save your shows to a floppy disk” you may be thinking. This is true, except for instances where said humans find your disk and overwrite whatever you had saved on that too.
Think it can’t happen? It’s happened to me several times. For one show our group was supposed to be the only one using the theatre, so in theory my precious show data was safe. Sure enough, when I arrived the next day after a long night of carefully crafting lighting cues, my entire show had been changed. I reloaded the show from the board’s built-in hard drive, but whoever reprogrammed the cues had also written over my save file. The show was opening in two hours, so I had no time to reprogram everything. Luckily I had saved an extra floppy copy and hidden it. That extra copy saved my bacon!
Always plan for the worst case scenario, which in this case is somebody erasing your light show right before you need it. Make an extra copy, and either hide it somewhere really safe or take it home with you. Doing so may just save your bacon too.