I have experienced a problem like this twice.
First time, my girlfriend let her car sit the first semester of college and when she started driving it the following semester she had some engine problems. We found a nest by the air filter and it ended up the mouse chewwed through one of the spark plugs.
The second instance wasnt as easy to take care of as the first as I am still dealing with it.
I was given a 99 VW New Beetle from my girlfriends uncle which had a blown engine and had been sitting in a pull barn for several months before I was able to get my hands on it. While taking the engine apart I would always think my mind was playing tricks on me as I thought I saw something move, IN the CAR! Sure enough a little brow mouse or two made home in the air vent intake between the hood and the windshield. It appeared several times throughout the overhaul and we thought we got rid of it and its potential problem once we had a new engine in it and had it running.
I dont know how long he had been living in there but everytime I turn on the vents/heat/ac it smells horrible like mouse piss. I have shampooed the car, used every form of air freshner and it still reaks! I am going to end up ripping the dash apart to clean that crap out, literally!
As for your chocolate, I bet he had a few friends help him out eating it. Even if that isnt the case, my hamster can eat more that its weight or atleast pack that much into its cheeks!
