Brake Pads

[Kanyon]

So since saturday night I've been hearing this squealing/grinding sound in the front end. Last night I looked at the brakes and found that on the right front wheel, the outer pad was completely gone leaving the metal back of the pad rubbing against my rotor. When I took the brakes apart I found that there is a small rivet or something that set right where my caliper piston pushes on the pad and it has chipped off part of the piston. (This rivet is on all 4 pads too) I took the pads and rotor back to Autozone and had them confirm that they were the right pads and they replaced them under the lifetime warranty. I wish I had pics to show, but does Autozone not know what they are doing or is there something that I'm not getting here. If someone could post a pic of what the back of the pad should look like it would help alot. I think mine were duralast semi-mettalic or ceramic pads. Also on the top of each pad there is a little tab, 2 are small and 2 are big, does the big go on the inside or outside of the rotor.

[Kanyon]

Crude Drawing

[BadFrog]

I dont have pics of the pad that go on our cars but I work at the place that likly engineered the brakes for our cars, the piston should go around the center rivet, if its not seated right you may need to check the little metal clip that hold the pad to the caliper. otherwise I would say keep moving them aorund till they fit the right way.
how bad is the chip out of your piston, it could be a problem down the road?(not trying to scare you but I test these things at work) get pics if possible