was the vascular tissue leading to it damaged? i'd probably give it 2-3 days before worrying about rotting issues, unless it clearly kept deteriorating and clearly dead.
i've accidentally damaged a stem, whether from pruning or just incidentally while reaching for soemthing else beyond it, and not realized it until the next day when the wilted leaves stood out... ah i nicked the stem, whoops.
maybe, it just got too dry compared to the rest of the plant and died before anything else did. more wind on that spot? warmer? it is in the middle, so it'd be a bit wawrmer and more light, which with no water would be more stressful? just guessing though.