It's their responsibility to do whatever is in the child's best interest, and they'll try to contact you, too. Airlines do not release kids to just anyone. Proper ID is required, even if the kids appear to recognize a family member. It's virtually impossible to put your child on the wrong plane headed to the wrong destination. Airline gate personnel always verify the information on the boarding pass.
Age restrictions keep little kids grounded.
A child must be at least 5 to fly alone. Kids 5-8 can take a direct flight to a single destination but not connecting flights. Those over 8 may change aircraft. If they're 8 to 11, they will be escorted by airline personnel to their connecting flight. A significant extra charge for this service is likely.