I have heard of "muscle memory" and one day I just drew a blank and couldn't remember the passcode for my iPhone, I tried with no duccess and I wasn't even going to contact Apple for help so I thought about it my right hand has put in that code so many times and I wondered that I wondered if my hand could remember the code without my conscious brain directing it and it worked. A friend of mine had the same problem and I told her to try what I tried and it worked for her too. Not exactly a scientific experiment but worth trying if someone can't remember their passcode.