Interesting Jeff - In the town of Redwood City, CA there is the old Main street, historically behind the stores was a slew or water way where small ships would dock to unload cargo. Let's jump way forward in time, and the slew had been filled in BUT the city needed to run a large pipe through that zone. When the city workers started digging up old bottles the place was opened up for the City folk to dig through. Many neat things were found. Then Franks Tannery used to be out on the mud flat of the same town, I believe it is now Veterans Blvd. Just Before the tannery was bull dozed I happened to go through one of the old warehouse/tannery building, there was an old steamer trunk and in the trunk was some stuff including a 1949 Centenial booklet (20 to 30 pages) of pictures and a small amount of verbiage about the towns history. A very handy source to indicate what was where and what mob figures were out along the coast.
Then of course the 06 SF earthquake and fire and all the burned down buildings and the dump grounds where all that burned stuff went, I mean it was just junk right! All sorts of coins, eye glasses, etc. have been found at that site.
But yes purposely buried money and/or valuables have been buried and lost everywhere over the years since man-kind started using "Money" instead of bartering for goods. I believe there are still plenty of finds out there, it takes research and work and some luck to come up with them...............63bkpkr