depends on teh situation
the adult in change is not always blameless
the adult is change is not always at fault
all depends on how it happened
what matters more is how the adult in change feels -- even if it is not actually your fault, would you feel it was?
Kidnapping is always wrong. Just like rape is always wrong, theft is always wrong, and murder is always wrong. It is never the fault of the victim, the victim's family, or the victim's neighbors. Unless they were somehow in cahoots with the perpetrator, it's not their fault.
It would make about as much sense to say "if your child gets kidnapped, it's your neighbor's fault." I mean after all, they gave the impression that they were watching the kids, right?