Sorry to hear about your snake! PetCo is sooo wrong when it comes to their reptile care.
First a few things to keep in mind:
What were your temps? How were you measuring them?
Since it was a 10gal, and the cage was by a window, it is a possibility he got too hot. A 10gal is a relatively small cage, and fine for a small snake, however if the warm side gets upwards of 90F, you can be the cool side isnt much cooler. This offers NO escape from the heat, and the snake can't thermoregulate.
In a 10gal tank, a UTH could have provided too much heat, and no place to really thermoregulate. If a snake stays too hot or too cool, it wont eat.
Please dont underestimate the importance of a humidity/temp gauge. Often heating devices suck the humidity out of a cage. What feels warm and humid to you, may be baking your snake..
Near a window is never a good place for an animal, as the heat/cold often seeps thru the window, not to mention if the sun is ever directly pouring through the window!
Before you get another snake, I'd invest in a 20gal tank, humidity gauges, and thermometers. The digital ones are best (Wal Mart
) Move your cage to an inside wall, away from drafts or direct/indirect sunlight.
Go for a corn snake, and they are a much hardier animal for a first snake..Not to mention affordable, and great pets.
Ball pythons are notorious for being picky eaters, and its likely this one was underfed from the pet store.
Let us know if you need any more help
