Question about dealership's responsibility of customer boats in for service

A friend of mine is having a few warranty issues done to his boat that's only a few months old. While at the dealer someone got into the dealership lot and stole stereo equipment out of several customer boats. The dealer contacted my friend and informed him of the thefts and said that their dealership insurance does not cover thefts involving customer boats. Does this even sound correct? I won't mention the dealership or brand but this dealer is a very reputable and one of the top dealers in this brand. He's bought 2 boats from this dealer in 2 years and I've bought 2 as well. They've always been amazing to us about anything boat or service related and get us in and out same day on anything. Just sounds weird. Thanks for any input.