Rootless noname oncidiums... help help!!

[zesty]

Hi there!
I'm very new to this site, but have skimmed a few threads before and they were very helpful! I'm hoping someone out there can help me with a new oncidium I recently bought... I'm fairly experienced with phals, and am fairly confident recognizing warning signs, so I figured I'd try something new in the orchid world and picked up a new oncidium! The flowers were beautiful, and it looked like it had lots of healthy roots, but once I busted open the pot, things definitely weren't right... it was PACKED with spagnum moss, and all the roots were papery, mushy and rotten! Now there are no roots, and other rotten spots at the base of the plant.. what now?! If anyone had tips on how to save this lil guy, I'd be very grateful!