Yup, you gotta get your treasure where you can find them. I've heard of the car wash vacs and having lived in Silicon Valley during the dot.com boom I'm no stranger to dumpster diving either, for "different" kinds of treasure.
I was one of the people who predicted gold going up back around 2000 so I started buying small lots. I was also paying 5-6 dollars for silver rounds at that time. A couple of years ago I started trolling the Goodwill and Salvation Army stores and actually found some treasures there in the form of gold, silver and rare books. Flea markets were also wonderful troves. I was buying gold rings for a song...until gold started swiftly rising which kind of ended that whole era, but not entirely. You can still get "deals" at these places but I haven't seen a decent peice of jewelry being sold at a Goodwill store for almost 2 years now, I'm sure they don't even make it to the display case anymore which is why it's really important to find one that has honest employees but those sources are just drying up more or less. Everybody knows that gold is really high now and they aren't treating it so lightly as they used to.
Anyway, so far I've had much better luck paying for some of my treasures in seeminly unlikely places than I have in actually finding anything in the dirt. All of my investments have appreciated, many of them several fold. I'm not giving up on MDing and prospecting though, it just takes a little more patience for those things, some solid planning and the ability to take the time which is the most valuable factor of all.