Don't think that these things don't happen every day, just ask Phil Coconis from autoMedia.com. After he parked his SUV in his garage mice ate through his entire wiring harness costing nearly $2000 to repair. Or you can read what Robert over at WombatNation had to say about what happened after he went on a 1 week vacation.
All in all, it does happen and as the saying goes, "One ounce of prevention is equal to one pound of cure." Let me show you your one ounce:

Before you pack up your RV, boat, cabin or car for the winter be sure you are taking the proper steps.
- Remove any food particles from the location
- Seal any exterior openings (roll up windows, close vents, etc)
- Place a Store It Right mouse pouch near any potential entry points, engine compartment, and interior areas to keep the mice away.
- Fill any gaps that are 1/4" or larger as this is all the space needed for a mouse to sneak in
- Remove any debris, grass clippings, bird seed, or other possible nesting place from the area