I can't believe that it doesn't occur to parents to put locks/bolts/latches high up on doors where little ones can't reach and to use the locks.
This did not happen at the parents house...it happened at a neighbors that they were staying with.
Again, common sense is seriously lacking in today's world.
That is why we have stupid lawsuits every day.
However, even the highest doorlatch can't protect a child from a predator if he is already in the house or if the child is outside.