the alarm clock incident

Today, I woke up and I looked at my alarm clock. I saw that it was about 5 minutes after my expected my alarm to go off. I was slightly disappointed thinking my alarm had failed to go off, but then I realized that I have the faintest recollection that I might have already woken up once this morning and already turned off my alarm. I can't be certain, but I'm pretty sure I had some form of amnesia.