Hrm... Did it look like this?
Or more like this?
Or possibly like this?
First one is just a white root. Phal roots are capable of photosynthesis, so most are green, but white roots can also be healthy. It just means that root didn't get a lot of light.
Second pic is an aerial root. They tend to turn silvery faster than the roots in the pot and can be brittle because they are dry.
Third pic, those brownish roots you see are dead, but not rotted. I have not reported this mini Phal yet. I have a pic of actual root rot somewhere, I'll find it and post it here.