Are
all the roots dried totally?
How long have you had it in the water? Try not to leave it sitting in straight water for more than an hour or two. I've left orchids in water for 12 hours and they've survived but that was stretching it. As epiphytes, they need air around their roots.
Can you get sphagnum moss? At the big box garden centers, it's sold in tiny bales labeled "orchid moss". Make sure the fine print says "sphagnum". If you can get to an orchid or other supplier that can get you long-fibered sphagnum from New Zealand or Chile, that's far better. If you get the sphagnum dried, soak it in distilled water until it absorbs all or most of the water - often overnight. If it's fresh sphagnum, I don't know how long you need to soak it (still figuring all this out myself). Cut off the phal's roots that are mushy and brown and then wrap the sphagnum around the roots with the sphagnum fibers oriented as vertically as possible, potting it that way. Don't let the sphagnum dry out all the way - just mostly, & probably water it with distilled water while it's still tender.
I'm sure many of the more senior members have better input than I do. Your new phal's so pretty - don't let it drown.
-Elaine