As a Pro user, you can create another instance of the game from the module, then use the Transmogrifier to copy the deleted map page into your original game. If you were a Plus user, you could create the new game and use Character Vault to move the player characters to the new game. If you were a free user you might be able to use the Character Vault depending on the module that you bought (some modules include Character Vault support for games based on the module).