Well I was driving I lost my brakes for a moment, then got them back shortly after. But now I hear a grinding sound from one of the back tires when the cars in motion. What could be the problem? When I went to press on the brake it went straight to the floor and I rolled through the stop sign. The brakes came back shortly after but now when the wheels are turning, it sounds like one of my back tires is grinding agents something. Nut I just had my dads friend do my brake pads no longer then a week before this happen.
Sounds like a brake pad came apart. That happens more commonly on rear pads when the car has rear disc brakes. The lining rusts off the backing plate and falls out. As you pump the brake pedal a few times, the piston self-adjusts out of the caliper, then you get the normal pedal back again. You'll hear that metal backing plate grinding against the rotor.
Be aware that once the repairs are completed, the master cylinder may have been damaged and need to be replaced. Crud and corrosion build up in the bores where the pistons don't normally travel. When the pedal goes to the floor, those pistons travel through the corrosion and the lip seals can be ripped. That will lead to a slowly sinking brake pedal when you hold steady pressure on it. When it gets worse, the pedal will go instantly to the floor with no resistance.