Why does nobody warn you about rodents in long term car storage

Did you notice any gaps or openings in that barn unit before you parked it? I'm asking because mice can squeeze through a hole the size of a dime, so even a tiny crack at the bottom of a door or where the walls meet the floor is enough. Also, was the car sitting on concrete or dirt? Dirt floors are way worse since they just burrow right up under the cover. And did you leave anything inside the car like snacks, cardboard, or old rags? Those things pull them in even if the building itself seems sealed.