Wow you sleep for 12 hours straight and your alarm clock doesn't wake you up? That's insane. If this continues maybe you should think about seeing a doctor because unless you've had some real lifestyle changes to cause you to need so much extra sleep I can't see any reason why this would happen. And I don't think it has anything to do with lucid dreaming.

How exactly did you manage to LD? Are you using an induction technique? Methods?