Hopefully you'll never need to perform action but if you do the following steps will allow you to revert a save on your PSVita to automatically created back up. I personally had to do this when my save file for Final Fantasy X HD got corrupted. I lost about 30 minutes of play time but that was better than having to start all over again.

1. First check to see if an automatic backup exists. They should be located at ux0:/user/xx/savedata_backup. You can perform this step and the next two from VitaShell.
2. Create a backup of the existing backup file, these are located at ux0:/user/savedata/xx/savedata/$TITLEID. Ensure to change out $TITLEID with the games actual title ID.
3. Next navigate to the games save directory - ux0:/user/xx/savedata/$TITLEID (again remembering to change $TITLEID to the games title ID). Go into the sce_sys directory and remove the sdslot.dat and keystone files.
4. Exit VitaShell.
5. Start up the game and you should receive a message about the save file being corrupt and if you'd like to restore. Answer 'Yes' here.

Source.