Cognitive Displaysia
Merriam-Webster has a compilation of words which aren’t in the dictionary, but are in common use.
To be honest, I’ve only ever heard two of these words actually used (’ginormous’ and ‘woot’,) but it does have one great entry:
cognitive displaysia (n): the feeling you have before you even leave the house that you are going to forget something and not remember it until you’re on the highway.
which is notable because I have this feeling every single minute of every single day, and now it at least has a name. Woo!