Thanks guys, I was under the impression that the alternator kept things going. After reading up on batteries in general, it looks like I hit the "reserve power" portion of the battery and that's why the car kept running. I'm upset that I trusted Autozone to read the battery and didn't ask what the volts where when the car was running. It was at 12.xx when the car was off but I'm not sure what it was at when the car was running, though the device said it was "good" but at 60% and not enough power to test the alternator.

I know its been said multiple times to check the voltage with the car running but without a meter of my own, I trusted Autozone's reading of the battery. I'm taking it to another parts store at lunch to charge the battery and double check it, hopefully the car doesn't die on the way there.

Thanks again guys