We often wake up at night and don't remember it, at least I do. One time I kept a notebook by my bed to record whenever I woke up at night. I made a note of at least one time when I woke up during the night that I had absolutely no recollection of. I often fall asleep with my light on, too. However, there are quite a few times when I wake up and the light is turned off. But I have no memory of having done so.