Why is someting buried so deep in the ground found metal detecting

Metal detecting out in the NH woods in old farm lands and in-between cellar holes. We are out relic hunting and digging up all kinds of stuff from the 1800s and even 1700s. There was also a hunting cabin on this site back in the 1930s and 1940s so there is a good mix of finds. New England has so much history so there is stuff to be found in the ground. Old coins and other artifacts are possible. So at the end of the dig there was a signal swung over and we started digging. We got down almost 2 feet in the ground and could see something big but we couldn't get it out of the ground. We need to know what could be buried in the ground so deep so we will be back next week with bigger shovels. Why is someting buried so deep in the ground ? found metal detecting Stealth Diggers use Teknetics metal detectors. The official SDNT website Check Out the gear & items Stealth Diggers recommend on Amazon