You have to meet the pig later and talk to him; then he will have a method to return to human form. I met him way later after removing the fire - actually he ended up near the dragon in this play.
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The dragon quest hasn't closed for me either but he did return to human form.
*Lizard.
And yes, I realize that there's more to it, but it was never indicated. The log says "you saved the pigs!" followed by "you talked your way out of the fight with Scapor" and then finally "the pigs are still burning horribly you sick bastard."
Or something similar. You get the gist of it. It's clearly wrong.