I have noticed that as well.
One time one of our dogs got out of our completely fenced yard and we couldn't find him anywhere, and it went on for a day or two before we finally found him safe. The feeling of guilt was unbearable, feeling we had failed at keeping him safe, feeling responsible for his life, etc. Whether there is much that could've been done about such a situation, or whether it is rational or not to be feeling that way, the inner feelings of guilt are unimaginable. I can't imagine the feelings of guilt one would have if they'd been in charge of a child who mysteriously disappeared, and even moreso if the child was not their own child, but tasked with that responsibility on behalf of someone else. To my knowledge I don't believe there has been ever, one mention from the FPs of feeling guilty, or even feeling responsible for this happening under their watch. But yet FM 'kicked herself' for not taking down the plate numbers on the vehicles she saw parked in the street that morning, and FD stated during the same interview that he felt guilty when leaving Kendall. imo.
From the FPs' two-part interview with Lia Harris one year after W's disappearance:
FM:
So it, it, it just didn’t make sense to me, that you know, I’m in Kendall, why do I think it’s an issue, because Kendall’s not the city, and I kick myself, I kick myself in terms of why didn’t I note down the, the number plates. But the logic part of me says you know what? In Sydney you’d write down the number plate. In Kendall? There’s no reason to write down a number plate. It is one of the most safest towns in New South Wales.
FD:
And all the way home, just a reminder, I mean I felt so guilty about leaving, there wasn’t, I couldn’t find him, just awful.
[part one] - permission has been obtained to post this link
