I had one like that, sphag and bag did not work for me too. I cut spike and misted few roots that left in the morning and evening, on weekends more often if I was home, once a week I soaked roots in rooting hormone (whatever you can find: kelpmax, superthrive ). Pot with rootless phal was standing in container over the water to provider little bit more humidity. In about 1.5 months it started to show sign of new roots growth.
So continue care for your phals as you do and be patient!
They will loose some leaves but new will grow !