Sorry for your possible loss.
It must especially hurt given that it was your favorite.
(I just discovered today that I almost certainly lost a seedling that I just potted up last week. On investigation the (not growing) foliage pulled right off and the crown was all mushy. I yanked the seedling from its pot, scraped out the center of the crown and rinsed it (and the roots), then sprayed an off-the-shelf cleaner with bleach over and in the crown, and left it out to dry overnight. I'm not expecting any miracles, though... but maybe (given that it is a seedling) it might be for the best if it is truly dead... we don't need to be propagating weakness. It galls me, though, given that it was - at least for another year - a keeper.)
