I got home and checked out the tires and was having a hard time finding anything wrong. Then, I got to the back tire on the drivers side and saw a pretty good sized rock wedged right in the center of the tread. It actually looked like it might do some damage to the tire if I didn't get it out.
Well, I couldn't pry it out with my keys, so I got a screw driver. Then that wouldn't work, so I got my hubby. He came back in the house and said he couldn't get it out either, but now the tire was loosing air. I called my dad and brother out with the car jack to change out the tire with the spare. I was dying to know what was in my tire so we pulled it out. This is what we found.
Not quite the rock I thought it was. I took a picture of it with a AA battery for perspective. I wonder what the odds are of picking up two very large fasteners in two different tires in the span of about one month.