It would be easy to miss just a few mites on a snake. If you're not certain of your examination, then that's probably what happened. Just a few mites that ended up laying eggs and producing more mites. The life cycle that was linked is similar to what I've read, and I've never seen any information that suggests the eggs will lie dormant.
Sorry to hear about your problems, I haven't had to deal with mites yet, but I'm sure it isn't fun.Hope they get cleared up soon!