Mice can get into the car through the garage. Mice often find a secluded place in garages. There are a lot of things, store food or pet food a place to hide, and also stored food. Rodents can get into the car through the suspension. they don't fit inside the car by details and can stay there. Tip: do not leave the garage doors open for a large amount of time, and remove all unnecessary junk from the garage.