I also found a DS not too long ago, I waa walking home and saw red in the grass, behold a Nintendo DS. It didn't work, there was no battery. I still have it, but I don't need it. I keep it in my junk collection. I feel that if someone lost it, and you can't return it, then just keep it.
Does anyone know if they can be rebooted, like how you can factory reset your phone? I found a cell phone one day and it had a pin on it. I literally couldn't return the phone unless someone called so I could let them know that I wanted to return it, but no one did. I reset it, and now it's my music phone. Sometimes you just can't get something back to someone who lost it.