I've put aerial roots into bark mix and that has worked well, but I suppose bark will be very different to sphag in that regard, drier and with more air circulation. Maybe you should try bark as an interim solution? Or mount it?
Because of my own stupidity and mismanagement I've had my fair share of rootless phals to do 'rescue operations' on. My experience is that they can start to shoot new roots from the bottom again...or...well, not QUITE from the bottom, but from below the lowest leaf at least.
Here's a picture of one of the phals that I nearly killed, and that is busy recovering.