I’ve learnt to scribble out the old reference in my notebook because I’ve done exactly the same thing. It was even the wrong association! Fortunately I realised straightaway and could correct it on air.
I think I need to go back to a bigger notebook. It was filled with pre printed sheets with the reference in a big box at the top of the page. This waterproof one is good but its I think I prefer A5 with the clipboard clip thing. To be honest am rarely out in the rain nowadays as I bought a bivvy