As you should! I actually have ancestors that were witches. Mary Este and Rebecca Nurse. Both were originally "Towne" sisters which was also my maiden name. Of course, they were pardoned after they were hanged, so I guess it was OK It's pretty odd to see a family tree that has "hanged for witchcraft" by some of the names.
Anyway, back on topic- Mold doesn't appear spontaneously. Cheese becomes cheeses during an aging process. It also has living enzymes in it (think yogurt) so, even if it is in an airtight container, it still will eventually mold. Cheeses mold at different rates (depending on the cheese) and some even mold on purpose and are edible that way. I doubt that any cheese packaging is 100% sterile and airtight. It also depends on the moisture content of the cheese. Cheese is just so complex.....