i have had the same problem about 6 months ago. I do not know what caused this. My front right inner pad snapped off and ruined my rotor completely. No warning at all. I thought it was just a bad luck issue but possibly not if you have the same problem. I have changed the rotors and brake pads and havn't had the problem yet. (knock on wood) I thought i would have had warning about the brake pads with the squeeker on them. but this doesn't help when the whole pad comes off.