Appearances are 9/10ths of the law. You can immediately give a child clothing, not touch them, and call the cops. I'd much rather stand in front of a judge on a frostbite charge than a child molestation charge...but the bigger issue is how unfortunate it is that you have to think about these things. When I told this story to my wife the absolutely first thing she emphasized was that you can NEVER pick up the child, even to help him/her. That's sad really. I don't feel good about it honestly.