My local Petco struck a deal with a breeder and has a bunch of morphs, but fortunately in this situation the manager used to manage a reptile shop and keeps them in far better conditions. She gave me 50% off my new (healthy) leucistic which makes sense for the store because they don't have to take care of it and wait for someone else to pay full price. I had the option of half off any of the morphs, pied included, but despite that being a more "desirable" morph I fell in love with the Lucy. The pieds sold out within the next couple of days, which this Petsmart was likely hoping for.

I think in these situations where there is a more expensive kind of snake the store wants to turn it and make a profit but ends up keeping it for longer because not as many people will pay that price right away so you see the deterioration that would happen to ALL of them if they were kept for a longer period of time. The store probably thinks you are just trying to get an expensive snake for free so it might be tactful in this case to offer them "something" for it, maybe offer to buy it at cost so they can just replace it (so it makes sense in their minds). The current snake could potentially cost them more in the long run as it needs medical attention so they could basically start over with a fresh healthy one. Not that I want them to but it might help you jump through those hoops.

I don't want the store to get spooked and just move it to the back and claim it sold when they're just hiding it so time is of the essence. There might be some arrangement that makes you look less like someone trying to take advantage but you might be the best judge of the situation.

As far as care, my baby from Petco retained all but its head the first time it shed so I had to soak him and help him shed, basically gently pulling the skin all the way around (thumb and index finger encircling the body - pardon the analogy but kind of like a condom ). The soaking also helps if there is any sort of impaction making the snake uncomfortable and not wanting to eat and the warmth feels good.