If it was melting his tub that problem would've been fixed in that day. And we would've heard about it, lol. I'm glad you decided to return the snake. For your next purchase go through a breeder. Even small hobby breeders are better and the prices are better since breeders don't try to make real profit from normals.
It's typically better all around because they can usually tell you the sex of the animal, how many times it's fed/shed, and you'll be more sure of it's general health.