How is that even possible?

So yesterday Tami called me and told me that the car was making a banging noise. I run home to check it out and I end up jacking up the car from every angle, driving around the block, bouncing it and even talking to it to see if it had any insight as to what was making the banging noise. I had the rear jacked up and I was checking out around there and noticed a little shiny thing right in the middle of the tire. Long story short this little shiny thing was actually pretty dang big and was hitting the rim every time it went around.