...and just recently, they just tore up about 2 whole city blocks, the main drag through town, to resurface...
diggin-fool, I can't believe you didn't hit that. You figured you could pick up bricks, but not detect? Sidewalk tearouts get detecting all time. If you wait for neon signs saying "detecting welcome here", and red-carpets rolled out for you, you might as well give it up and sit at home