have you tried calling local animal control to report the store? I filed a complaint against a store when I lived down in SoCal, it didn't really 'fix' all the problems, but an agent went to the store, talked to the manager and the store knew they were being watched. They cleaned up a bit and at least started taking the dead ones out more often. You could also file a complain with the better business bureau or even the local news! If you have photos, it helps.
Pet-Abuse.Com - Reporting Pet Store Abuse and Neglect
Buying or 'saving' the snake really does nothing other than make the store money and then they'll just get another one to replace it. As sad as it is to walk away from that type of situation, sometimes it's best. Also, I thought it was illegal for dogs and cats to be sold in pet stores here in CA?