Harassed on the way to the nats?

Be careful how much of a nondescript of a car you drive. I was driving my mothers 97 Neon through the town I work in about two years ago. It's losing the paint on the trunk lid and sort of looks so-so. I got pulled over, for no apparent reason by a marked car that followed me about two miles. When the officer gets up to the door he says I don't have a front plate (true). There are lots of cars without front plates, some of them in the parking lot at the police station I might add that the cops themselves drive. Anyway, I get a warning for no front plate which is fine, but the car has never had one, came from a state that didn't use them and has no bracket. Never been stopped before until the paint started to flake off. He was obviously profiling for insurance violations. I gave him the reason he needed by not running the front plate. I guess people that drive beaters don't have the money for insurance either.
Maybe a stupid question, but how did he know you had no front plate? following you?