Did you inspect the animal before you bought it...?
I would imagine, had anything been noticably wrong you would not have bought it...I suppose you need to consider, if you didnt see anything wrong it is probably not unreasonable for the seller not to have seen anything wrong...
...I certainly agree that if a seller passes on a sick animal to you some sort of recompense should be made...
If you did not inspect the animal, or noticed something wrong and still purchased it...well, it's your issue to sort out to some degree...
I have had one sick snake, he got sick somet time AFTER coming into my care (an RI which he has since recovered from), however, the person I purchased him from offered to pay my veterinary bills if I thought it was sold to me with the RI...of course I didnt, and as such turned down the offer...this is a fantastic example of a seller, however, I certainly dont think there was any obligation on him to make such a generous offer....
...just a little reassurance than many breeders out there ARE good and trustworthy...
Also, it has been said that this should teach people the lesson "DON'T BUY FROM SOMEONE YOU DON'T TRUST" - ...I must say, that if you willingly purchased an animal from someone you knew had a bad reputation or you did not trust, well, again, a lot more of the fault must be accepted by the buyer...