I'm not pointing fingers at anyone, just playing the devils advocate here.

Since you live an hour away, I take it this deal was done in person. Which means you actually had all the chance in the world to look at the snake with your naked eye and still took it without questioning anything, which means at the time the animal changed hands it appeared to be in good health. If the deal was a third party (Fed-ex or UPS) deal and shortly after it arrived you noticed something that would be one thing, but it doesn't sound like the case here.

Did your witnesses go with you to do the trade?
Was the animal observed by a witness from the time the trade took place to the time you noticed the scale problem?
Was a cause of death determined forensically for the snake?

I think your case would be very difficult to win in a court of law since something as simple as leaving the sun bake the snake bag through a window for an hour long car ride can cause significant damage to scales. (Not saying you did this, just bringing up possible defenses.)

Also if you go to court you could find yourself in a counter suit.