If you're on FB there's a post now about a BP at the Bravo Ft Wayne, IN Petco in similar shape - dehydrated, thin, stuck shed, RI, and mouth rot. OP didn't buy it, but Petco corporate will have a lot of emails from PO'ed people from around the country tomorrow morning.
I understand the sentiment of wanting to get an animal out of a bad situation like that, but the seller shouldn't be rewarded. Either get the store nailed for neglect by the authorities, or raise such a stink right there in front of the customers that they just give you the poor thing to make you shut up and go away.