Squeaking/squealing could be from just dust, a small rock stuck behind the backing plate, etc. Like the others, I would be shocked of the brakes were gone. I would start by pulling the wheels off and looking. If the pads are still good then I would remove calipers and remove pads from them. Clean pads and calipers real well, and then apply generous amount of disc brake lube to the back of the pads anywhere they contact the caliper. Reassemble and you should be nice and quiet.
The squeal isn't from surface dust on the rotor. Its comes from dust getting between the pad and caliper. The pad vibrates just a tiny bit against the caliper causing the sound. When I was a shop monkey we had more people come in certain they needed brakes, but just needed a clean and lube.
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