I would venture a guess that your TV was in a lot NorthWest of the stadium. Standing (or sitting in a car) w/ and antenna there would put the gigantic stadium between you and the broadcast tower (blocking and reflecting signal paths to your antenna). I would still expect that if you aimed an antenna (or hell a coat hanger) SouthEast you'd pick up the CBS feed without too much problem. To the original OP, if you stay West of the stadium, I would expect that you should get reception of many of the local stations.
I have recently moved away from cable/satellite and have been exclusively OTA. As a result I wanted to make sure that I would get as many OTA stations as I could (hence radar plots). Oh and I'm a gigantic nerd .