A British farmer lost a hammer in one of his fields one day. Rather than going to spend a few bucks to just buy a new one, the man borrowed a metal detector and set out to find his hammer. Instead, he found something much more valuable. What he unearthed was a cache of Roman Empire era artifacts. To be exact, 15,000 coins of various metals, including gold, as well as jewelry and statues were all uncovered.
People go to garage sales and estate sales all the time. Some get really lucky. Here's a few stories of people who had something they thought was worthless but turned out to be worth millions of dollars.