When it comes to writing, I'm not much of a "linear" thinker. That doesn't mean that people who write like us don't think. It's not like I think I'm a conduit for "God" or a muse or something. Like you, I have odds and ends that come to me, and I'll save those in a doc for future reference. But a lot of description, symbolism, dialogue, etc. comes as I write, in the moment, though I USUALLY have a general sense of where I'm going, even if the specifics don't come until the vomiting stage. ;)

But I have the sense that maybe I could make the process more efficient -- and possibly make the product better -- if I molded myself into more of a planner/outliner. I don't know if that's right, and the point may be moot if I just can't make myself work like that. And yes, for a casefic, it's practically necessary, unless you want a gazillion drafts.

As for your putting notes in your phone, hey, a writer's gotta do what a writer's gotta do! :)