anyone know how to find a private number?

heres the deal, i just got a call from a private number, telling me i had a pizza being delivered, in columbia missouri. however, i don't live in columbia anymore. these were obvious scammers, and i'm just wondering if anyone knows how to find private numbers. i hate these guys, and want to see them be brought to justice. (this could just be me being pretty p'd off though.) this doesn't seem like something any of my friends/enemies would do down there, but i don't know. they called me telling me they'd be outside my place in 2 minutes, and that it had already been charged, when they called back they said they would credit my account. sorry, just a lil upset over this.