Hmm, that's too bad you had to throw your first batch away, what happened there?
Valley Fever appears to be something you get from breathing in spores of a fungus that may not even be able to grow on food, and only releases spores after a rain in desert areas. You'd be just as likely to get it sniffing your leftovers to see if they're still good. And you can still get contamination no matter what method you use.

Besides, my cakes weren't contaminated. Two were initially, with mold, but I cut that part out before it could get much bigger than a pinhead. Plus, I've heard that if the mycella beats the contamination, the resulting mushrooms are ok, as long as there's not stuff growing on the mushrooms themselves.