Muscle memory is an amazing thing. That kind of unconscious memory is the reason why it's said that you can never forget how to ride a bicycle - though I can't verify this for myself, as I never learned to ride one in the first place. (I have no sense of balance). My conscious mind forgets all sorts of things (like my doctor's appointments and how much hair I have), but my body still goes on, doing what needs doing.
And now I'm sitting here with wet hair unable to go to bed because my damned conscious memory forgot that I lent my hair dryer to my mum a couple of nights ago and that I hadn't asked for it back yet! Argh!