i would keep him, and publically shame the seller.
for the snake, i would say permanent residence it is. its yours, deal is done, every snake needs a home.
for the breeder, communicate with him, and if it doesnt work out then name him, and shame him, publically. put it all over the internet that this is a douchebag who cuts corners, and who sells hatchlings before they had their first meal. and make it known that he lies about the BPs he sells. that includes naming that bad apple here. maybe he just screwed up, give him the benefit of the doubt, innocent until proven guilty, but if his response to make this right is unsatisfying, then keep the snake and go and destroy his reputation. name him, his real name, name his website, and shame him.
the only reasons not to publically name, blame and shame him would be: Missing information, or Cowardice on your end, or pending lawsuits and trials.