There is a backup file in your Virtual Villagers folder, but it won't be as current as the one that you deleted. The savegame files are Isola**.ldw (where ** is a number). The single-digit numbers are your "primary" savegame files and are numbered 1-5 (corresponding to the player slots). The two-digit numbers are the "backup" savegame files, and are numbered 21-25. If you rename the backup file that corresponds to the one that you deleted, you will be able to recover that game to a previous point in play.
The savegame files are ordinary files that can be backed up in a safe location of your choosing. Just remember to pause the games first, or you may be greeted by an unpleasant surprise if you ever need to restore one of them.
