Contrary to what I might have thought, I did write an outline once, and it seems pretty good, but I wrote a different story because it was too detailed to review nicely. I had a clear statement of theme, notes relating the characters to the theme, a four-scene outline with detailed scene notes and blank spots for another scene or two and reasoning about the structure, and whole paragraphs of backstory.
Unfortunately, I didn't review any of this, because it's a bit too much and too unstructured to review. As a result, the scenes I wrote diverge from this outline, at first lightly and then greatly.
This suggests that it might be good to separate my outline from the detailed notes. If the plan ended up useless because I didn't reread it, I should cut it short and put the long plan somewhere else. If I care to, I can review the long detailed plan while I'm editing the story. And if I don't, that's okay, too. The outline might be more important.