YES YOU WERE! The noise is just a little piece of metal that makes a sound for you to check brakes before ruining the rotor. Please google how to check disk brakes - it is very easy, and easy to replace by yourself also.
See that little groove? that's your check. First the groove is worn and the last chance warning it the little piece of metal that make squealing noise that reminds you that have to change brakes ASAP before damaging rotor. and uh .. change your mechanic -the guy SUCKS. I would post on ripofff.com compliant site so that others don't get ripped off. Here is my story about getting ripped off here: http://hub.me/aewKm
You are not going to get your money back but at least get some emotional satisfaction for pitchin' a bitch.
Oh, always ask for the old parts in the future
So if you are riding the brake at all times and your brakes are truly worn out, sliding the little metal groove out is not a fix but yeah would have to change rotors if metal to metal.
Park car with wheels cocked to one side. Remove tire, check through inspection slot for yourself.