First a little background. We have a shed/barn that has a room with a concrete floor. It was originally a tack room for storing saddles and bridles. My son has fixed it up and has his Xbox and sound system up there. It also has an internet connection. He plays games with his friends online well into the night. This is good because I don't have
to listen to his games or music.
A week ago, I was having a campfire. My wife came out and we sat around until well after dark. While we were sitting there, she happened to mention that he had told her that he saw something fall from the sky and hit the tin roof of the barn. WHAT !!!! He didn't even mention it to me. If it hadn't been dark, I would have grabbed my
detector. I went up to the barn and interrupted his gaming and had him tell me about what he saw. He was walking back to the barn on the 10th or 11th at about 1:30am. He was about 50 feet from the barn when he saw it come in at a low angle from the southeast (to his left). He said it looked like a tracer bullet, glowing red. He heard it hit about in the middle of the tin barn roof and bounce off the edge. He said it sounded like it was bigger than a BB.
Of course, I was out there first thing the next morning with my detector. The area is so loaded with iron that the detector was getting too many hits even with a small coil. I thought it might have bounced to the back side of the roof so I went to the back to detect. There is a concrete pad on the back that has wire mesh in it so the detector was useless. So I put a powerful magnet from a hard drive on a stick and started sweeping the ground. I knew it would be on the surface since it had rolled off the roof and had only been there a few days. After a half hour on the back of the barn, I went back to the front and within 10 minutes I had it. Right where he said it had hit at the center of the barn and about 3 or 4 feet from the front of the barn. He was pretty close on the size too, it's about 5/32" (4.5mm), slightly larger than a BB. It's almost perfectly round and the surface is pockmarked.
When I first talked to him about it I tried to impress on him the odds of this happening. I can't believe he didn't even mention it for a week. He was more astounded that I found it. That was the easy part.
I suppose no point in owning a firearm if you don't know how to use it. 
