Sleep doing stuffs
I can see entirely how somebody might wake up, do a semi complicated activity like this, then go straight back to sleep.
Consciousness is not 'entirely' an on-off switch, I feel like its more of a gradient, with a kind of consciousness cut off point (If that makes any sense) that seems to vary depending on tiredness levels, for me at least, and the amnesiacal properties dont seem related to any particular level of consciousness either - not that I could argue this part very well!
I've awoken at some dark hour on many an occasion, sometimes to go and get some painkillers or something, you feel so drowsy, consciousness verging on non-existent, like you could just slip right into unconsciousness in an instant without even wanting it to happen. I see no reason at all why I couldn't ever have done an activity like this without realising afterwards.
I remember seeing some sleep-scientist type on TV - a presenter/reporter of a show covering some sleep related article swore blind he was awake throughout a sleep experiment he partook in, but then some arrogant scientist looked at an ECG reading or whatever, and decreed him to be asleep! "No you were actually asleep.". "No I wasnt!!".
I mean how arrogant must they have been to think its just a simple on-off switch? I'm surprised that so many people still see sleep as being so 'boolean' in nature!