I have had my clay pots dry out very quickly and I simply had to bring up the general humidity so that the pots weren't being sucked dry by the atmosphere.
If you are growing inside and running a heater you definitely need to augment the general humidity or the clay pots will get dried right out. You really need to repot that orchid. I would clean all the roots with a solution of bleach water, about 10% bleach, trim off all the dead rotting roots with sterilized tools and repot with all new mix and a new pot, too. In general, do everything to save it that you have, or, will read on this forum. Good luck, Remo.