That can happen when the potting mix stays too wet for too long. Roots just start to die and eventually you are left with either rootless or dead plant.

You have one good root, then it should grow fine as long as you give it a good care.

I find the mini's a little harder to care for than the big phals. They seem to dry out faster but yet I think it is easier to over water since they are so small.

Sounds like over-watering. Was the moss always wet?

If they are like the mini Phals I just recently got, they are in very tight sphag with one hole on the very bottom of the soft pot and then in a tiny tall little cache pot. Really no way for the roots to breathe at all. I slit the soft pot and removed a good amount of sphag and then set it back in the cache pot. If I re-pot now, they won't fit back into their cute little pots so this will do until they are done blooming. Then out of that tight little pot and into a larger clear one with holes and a mix of sphag and bark. I still don't use a large pot, just big enough to fit the roots.

This is what I do, well I don't take any spagh out of the pot. They seem to do fine once I make slits in the pots. I have 4 of them, and they have all grown roots that will push them up out of the pots. Then I pot them up just like silken. 3 of them are going to bloom soon.

I just seen them at Walmart , and glad I ran a cross this thread, of great help.