Well, you said Petco advises this treatment, but really it's just this one associate from this particular store. Actually, on the Petco BP care sheet it just says to take the snake to a vet if they have mites. Every Petco is a little different, and it doesn't seem like this particular store takes very good care of its ball pythons or its mice for that matter.

What did the mouse look like when you bought it? Did it appear alert and healthy, or lethargic/sluggish? Did you notice any abnormal feces? How about the mouse setup as a whole?

Snake mites are not the same as mouse mites. I don't think snakes can get mites from mice... but correct me if I'm wrong.

I'd go to the vet ASAP, or if your animal is still under warranty (15 days from Petco), I'd take it back and get a refund. You're better off buying a snake from a reputable pet store or breeder.