It's true that a lost dog is easier to get returned, because it has a tag! I have personally experienced being a lost child. Two stories come to mind. One is my grandfather "lost" me at the race track when I was 6. Good thing there was a helpful lady, because my grandpa didn't speak english, but knew to to go to a police booth. Another is when I took a walk around the block and couldn't recognize the house (we just moved in). Good thing there was a nice neighbor who took me in, because my grandma didn't speak english. It turns out that I was next door!
Kids used to have tags on all their school belongings- jacket, books, with their address on it. Until everyone can afford to have a GPS [some day we will all have implants], a simple tag with a cell phone number with a "Return to / In case of Emergency" is the easiest solution.
And every child that can should always know where to meet at certain times- amusement parks, mall, open venue. As well as the ONE emergency/evac point in case of a major disaster.
Lose the dog, not your child!