I'm almost 100% sure, the mites Vincent had where from the pet store. The vet said it takes mites a few weeks to hatch, so they were probably just eggs when I bought him. My next snake I got from a breeder and never had a problem.
I just wish I could stop quaranteening them. But their health is more important than my joy.
To the post above mine (JLC): I thought PAM just stuck around long enough so when the eggs hatched the mites would die as soon as they were born. Maybe this isn't true, but it's still AWESOME.