I had fun with that writing prompt. The story pretty much came out the way it ended, with a few small detail changes. My muse says I should finish it. :)
Half the time I think something's finished and it turns out not to be, the other half I don't think it's finished and it morphs into a series. With short stories that's not such a big deal. With novels, it can be.
I need to figure out how to evaluate a plot. I can do it on other people's work, but for some reason I can't see the problems when I try to evaluate my own. Maybe because I'm just too close, and possibly because of the way I write.
My first drafts are very organic, developing as the characters walk through the situation. Life doesn't have foreshadowing and plot discrepancies, and these novels develop simply by the characters doing what comes naturally. They change a lot in revision, as I put in foreshadowing and new plot arcs, build new characters or lose them.
In revision as well, sometimes it turns out that I have more than one story that I've tried to cram into 70,000 words and sometimes I realize that the story itself isn't finished.
Live and learn, I suppose, but in this case I wish the learning would go a little faster.