Professor McGonagall didn't know that Hogwarts had a Failsafe.The Spell she used to protect the students triggered the castle to protect itself. It's been creating labyrinths. Some of the loved ones of the missing ventured in, never to be seen again. It's like they never left. Draco Lucius Malfoy, the verdict alteration comes with a stipulation that you must return for the rehabilitation of Hogwarts.