Ive seen this kind of stuff on craigslist, ebay, gumtree, even some guitar and music shops that sell used gear but i wouldn't be surprised if there's no paper trail and is sold by word of mouth. It may have also been stolen to order if its good named stuff. Without reporting serial numbers as stolen to police then you don't stand any chance of getting them back. Good guitars are either stripped and sold for parts, amps the same, piano's, keyboards and PA stuff i'm not as au fais with. Keep an eye on the aforementioned sites though.