I definitely agree that our brains work wonders and I'm not denying the main point you're making at all, but there is also an element of confirmation bias inherent here because you'll never look for the notes you don't remember taking. Going over old notebooks I've been astonished at the patterns I've uncovered of thinking about similar ideas and having similar insights over and over, each time not recalling that I've been on the same path at an earlier time.