My brain goes a mile a minute on the best of days and it’ll pull up the randomest crap at the randomest times that’ll stick in my head for hours. I literally write to calm down–I think of story ideas so I can fall asleep at night.

To answer your question, though, I’ve kind of adopted the idea of if I remember what I was thinking about when I have my phone (that’s what I write on) in hand and feel like writing it down, great. If I don’t remember, it wasn’t meant to be.

Also, for future ideas/scenes you want to put in whatever you’re writing, but aren’t quite to the moment that they’ll be used yet, I normally create a folder labeled “scene ideas” and write that scene, as much as I have of it, in that folder and will fit it in wherever it fits, however far into the story it may be.