I'm sorry about your poor little orchid! I think the fact that it's growing a new leaf is a good sign though. If I understand correctly, at the moment it's bareroot on a saucer? If so I would increase misting it to once a day. If it's not in any medium there is really no danger of overspraying as long as you do it early in the day. Keep it in a warm area and maybe think about putting it in a big ziplock with some wet sphag at the bottom or moist paper towels. Make sure you open it every couple days so things don't get moldy. Lots of people on here have great success with this method. Hopefully someone with more experience than i will chime in. I'm no expert!
I would follow this advice. I have found most Phals to be way more robust than one thinks and I'll just bet (keep in mind I'm not a betting person, but this is a sure thing) it recovers. Don't expect miracles overnight. Try this regime (besides Sarah's advice) use KLN mixed 2 drops per quart in a quart sized spray bottle to spray the whole plant, leaves and all (including the one viable root) every single morning early. Let the whole plant dry off before evening. Watch for little nubbins (Dorothy's term for new roots) to occur near the base of the plant. Keep the plant in shade (not real dim light - just no sun). Short of this try one quick spray with KLN then place in plastic bag to hold humidity. Add a small wad of wet moss or wet paper towels - not touching the plant. Mostly seal the plant but keep out of sun. When nubbins appear start the KLN daily routine. One of these should work.
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