Shh… tell no one
Wherever there’s food, there are rats, and there’s no way to escape it. You can set up rat traps and other things, but rodents will always find a way to snatch whatever grub they can get their paws on. Remember this is the next time you go to a restaurant or even a movie theater.
According to the OP who worked at a theater, they discovered tiny holes in the unopened popcorn bags. Where did they come from, you ask? Isn’t it obvious? What’s even more disgusting is that the manager taped the holes shut instead of tossing them out as any sane person would do.