On this web page - http://www.chulaorchids.com/html/phal_help.html - I found the following interesting advice. This is just an excerpt from the full page, offered here for your comments; and I'm wondering if anyone has ever tried this. I might, the next time I want to buy a sick plant. I wish my stores around here would give discounts on the sick ones. They don't, because they get credit for the ones they send back to the growers.
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Every time a customer showed up with a wilted plant, I would simply ask if we could check the roots, even when they told me they did not water too much. They were amazed as we unpotted and found this wet glob on the bottom of the pot. Repotting cures this.
But if the plant has lost nearly all of its roots, and is badly wilted you have a 50/50 chance of losing it. The best chance for recovery is back to the basics. You can use the biggest clear plastic bag you can find, like a turkey roast bag or a large clothes bag. Sit it on a counter, put a bit of damp moss, probably will need a wire or stick to hold the bag up, and put the plant in the bag pot or no pot. Use a a patch of moss perhaps 1" x 4" long, not drippy wet, just damp.
If you unpot one and it has no live roots take the mix off and put it in the bag bare-root. You can put several in the same bag. Close the bag except for perhaps a one to two inch opening at the top. Hang the bag it or sit it somewhere that it does not get direct sun but stays above 65 degrees and leave it alone. The plant should start new roots right away. When the roots get to be 2 or 3 inches long you can repot the plant.
The intense humidity the plant gets in the bag is like it was being raised from a seedling, warm and cozy, no watering just misting. You won't have to mist at all in the bag until you see no condensation inside the bag, then may be a short dip of the moss, squeeze it almost dry and return it to the bag and it will be sufficient. Forget about fertilizing while in the bag, the plant probably has no roots to take up the fertilizer at all. The goal here is to grow new roots, then back to the pot using the types of mix listed above.
Phals will grow in many different mixes. The key is to learn how to water the plants for whatever mix you have chosen so that the roots do not get too wet. It must drain well to let the plant thrive.
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Interesting phal hospitalization advice
Sounds like good advice to me!
It's an old concept called "sphag and bag". It works well when ambient relative humidity is low but you can set a plant on a styrofoam tray with damp sphag in warmer, more humid weather and have greater success. The reason being better air circulation outside the bag. The bag method will be more likely to create an environment conducive to bacterial and fungal disease. Though the sphag discourages growth it does not prevent it.
Yes sphagnum moss promotes root growth and is good to use on a orchid with no roots but those roots are usually lost due to the moss and being kept to wet. The key is to not keep it wet and yes you do need some air flow in the bag.