I didn't mean to start a firestorm but it's not hard to believe. It just proves that you never get it all. I've followed behind guys before and picked up a slug of coins they missed. I trailed three guys one time and picked up about $2.50 in coins they had missed and they were walking almost side by side. When I showed them the coins they refused to believe it. There is no way any detector in the world can cover every square inch of turf no matter how wonderful it is claimed to be. I believe I have an article on that very subject in the Online Magazine at TD and also an old issue of Lost Treasure or Treasure Facts, complete with diagrams.
There is an old park a few blocks from my house that I have hunted for 30 years and never found a gold coin but other guys did, detecting in the very same spots I had covered many times, and one guy that found a gold coin was using an old TR machine. The only way one could completely cover every inch of any area would be to dig it up and methodically sift every square inch of soil several times.
I once conducted an experiment then wrote about it in Lost Treasure. I visually staked out a small area ( about 20' x 20' ) then hunted it north to south, east to west, then hunted it diagonally from each corner and found coins and trinkets each time that I had missed going in the other directions. I also overlapped each scan by more than 50%. As I recall I pulled over $7.00 plus trinkets out of that plot. I done the same thing on a grassy knoll in front of a high school auditorium and pulled out over $13.00 in coins, a bracelet watch, two gold rings, and one silver ring, plus other trinkets. It is very time consuming but very productive but most people don't want to spend that kind of time and effort, they want instant results. Your hunting style, method, and time spent, has everything to do with what and how much you find not the detector you are using.
Bill