Well, my story did not win. Not even an honorable mention to speak of. I attribute this, for the most part, to two circumstances:
1) Procrastination. I had three weeks or so notice about this contest, but except for the most cursory of preparations, I put off working on the story until the weekend that it was due. I also forgot to write down several thoughts I had percolating in my mind about the story, and I'm pretty sure my story suffered for their exclusion.
2) I bit off a bit more than I could chew. A situation like this one - only 250 words - more or less requires an eschewing of the normal idea of story; this allows only enough time for a snapshot in time, a glimpse of a few moments, and some of the story must remain untold. I thought my story did a fairly good job of this, but not nearly good enough. I think I needed more vivid description and less scaffolding.
I'm also left with a sneaking suspicion that the judges, overburdened as they were, did not pick up on the symbolism of the rainbow/Covenant with God theme I was seeking to examine. I think I might take the opportunity to re-write this story without the 250 word restriction and see how it goes.