In my list of blog post ideas, I have an entry that says, "The lesson is for yourself." I have no clue what this means. Like, I can think of a few possible ideas that might stem from it, but the original spark that led to that note are gone and forgotten.
When writing from session to session, it is great to have one in the chamber. When you know that you have an idea that you can literally sit down and start working on, you will be off to a very great start. However, if your idea is so incomplete that it doesn't help you to write with any focus or clarity or inspiration), then you have nothing more than a flash in the pan.
If you are leaving notes for yourself, whether it is something you get back to in a couple days or ten seconds, give yourself enough to work with. An idea without substance can be worse than no idea at all, because you may end up spending far more time and energy trying to reclaim that idea, despite only being able to grasp at wisps of memories.