Hmm -- probably right. Which means that either petrification is impossible here, or it's as one-way street, with no magical way of revival. Useful. The errors of common mundane knowledge about magic are a minor thread.
They will dispute a bit about various aspects of the tale, such as whether you can really be turned to a snake, and whether it's possible that even if no sorcerer knows how, one might discover how to do it.
Sometimes the world-building clears up itself.