Cool article. My grandfather and his brother owned a junkyard/car repair shop in the Boston area from the 1920s until about 1970. My brother and I happened to go by there last summer and were talking to the current owner of the property. Seems he unearthed a transmission while digging a post hole once, and, while trying to dig another hole to put in a tree, found the hood of a car.
Needless to say, you can imagine what ELSE might still be in the ground there...
I read somewhere, maybe here - this guy said that he ran a car shop a long time ago, and his father or somebody basically sealed up a nice car in the walls of the shop. It was later sold but they went back years and years later and it was still there.