Could have been anything. All it takes is one mite or one egg from anywhere and they spread like wildfire. I got them from a couple new snakes I got for Christmas and the PAM cleared everything right up within a couple days. Good luck.
And one can goes pretty far. I still have about half left and I have 17 snakes and my beardie that I treated the enclosures with. Not sure if you have any invertebrates, but be SURE you don't spray anywhere near them. I actually temporarily relocated all my tarantulas to a closed room for a week while I was treating, apparently it kills them too.