Papa Bear said:
Hold on......You are only allowed to dig so deep

You must understand it this way, Papa Bear.
I am an amateur archaeologist "working together" with the museum.
I get a fee for my finds. In my country you have to send in all finds older than 1536.
I can search an dig in the plow soil. If there is nothing more that the detector can hear, I must wait til next year when it gets plowed again.
But when things are deeper down, like at coin hoard might well be, the archaeologists must come and make an excavation.
In this case with a hoard, I will get a fee also for the coins that may later be found by an excavation on the location.