I have the bird thief quest and have completed most of it: found the trapping site, brought a bird to the old man, etc. The old man told me how to cast the spell. The guy who gave me the quest lives at a small settlement with no sauna, so I went to the nearest village, lit a fire in the sauna, then threw the three feathers from the trapping site in the stove after it burned out.
Several days have passed since then; I would estimate a week and a half or two weeks. The bird thief still hasn't confessed. Did I do something wrong? Does the spell have to be cast in the same village if you do it in the sauna? I can't cast it on base rock because the ground is hidden by the snow.