I live close the the St. Louis area and I will tell you, No park is hunted out. Here is something to think about, I won't even go into the 20 million people that showed up for the worlds fair here. Understand this park is one of the biggest parks in America, 1293 acres! How long would it take to cover that area , inch by inch? Do you know the events that go on there even today? It rained yesterday here so the turn out at one event was only 5000 people. There are around 12 million visitors there per year. Now even if you looked at "todays" losses only, it is overwhelming what is there. And most of us hunt parks or old home sites with a few hundred, maybe thousands with local fairs and such. We are talking millions per year here.
Most of us sould know.... have faith in your machine, understand what it is telling you, hone your skills, and use a different approach...maybe hunt across the path rather than straight down it....and see things differently. I have only lived here about 2 years now and know for a fact, We never find it all.