As long as the family that has the kitten now is a loving responsible family, I would say you did the perfect thing. Who on earth could know that someone might come back for a kitten in a cabinet. And any way, if that is how those children are taught to care for their pets, I don't think they are learning and this might be a lesson. If that second set of children are interested in findaing that kitten, they can certainly ask around, right?