I don't think enquiring about the welfare of the kid is out of line. A simple 'he is living with a relative', 'foster care' would have sufficed and would not be a breach of privacy. You told an interesting story and it's completely natural people are curious how the situation unfolded.

The story is about the father, the fact that he had a child figured into his reasoning (and in the wrong way) which is why I mentioned it.

It's a small world and not all curiosity is good, the basic story does not change and the whereabouts of the child are about as private a piece of information that I possess.