This morning, at 6:30 AM, as I backed the car out of the garage, I again heard the FWAOP FWAOP sound and I again stopped the car. This time, apparently, I stopped in the right spot and was able to see this...
Please forgive the photographs. My tire-photo-taking-in-the-dark-skills are sadly lacking. That is a bolt. A big ol' bolt with a washer which I somehow managed to run over.
Thus beginneth my day. How's your day going?