My daughters exited the room where they were supposed to acquire the Reducto spell and continued the game without it.  They can progress further into the game before getting it, but when they return to the class where they were supposed to learn the spell, it won't offer them the chance.  We restarted the level without saving, and the game still won't let them get the spell.  Is there a way they can back track and unlock the Reducto spell?