User blog comment:Hermione Chase/"The Blood of Olympus" Expectations/@comment-24404080-20140304192821/@comment-3146930-20140305042252

The only way that would happen would be if Luke was already in Tartarus trying to escape the Underworld and found Annabeth's knife on the way to the Doors of Death. He is a child of Hermes, so he could slip into the elevator and escape without being noticed maybe, however unlikely that may be.