So your neighbor hung up to proceed with a follow up call, which, if they're like most people, consists in just pressing the switch with a finger, while keeping the handset to their ear. But then upon releasing the switch, they just started dialing without waiting for the dial tone? And after they finished dialing and never heard the ringing tone, they didn't find that unusual? Forgive my skepticism, but something's missing from that story.

Edit: Just read up on the disconnect time (10 seconds for some providers) and yes, a sophisticated scammer could indeed emulate the various tonalities.