It could happen. Maybe it just just a few that got out and hid somewhere untreated and then they multiplied until they were noticed again. Here's a really good write up from VPI on them.
http://www.vpi.com/publications/the_...of_snake_mites
They obviously came from somewhere and I've seen mites hid out on racks etc and then boom you've got a problem. I have not personally had a mite experience but I watched a very good friend of mine struggle with a serious mite issue and everything in the entire room had to be treated with Pam. Not just the sub but entire rack, wires, thermostats, etc.
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