Would you say to that person "I think you should be reported to DOCS for letting that happen"? I don't think so. We'd all understand how things like this can happen so quickly and so easily. There have been more than a few well regarded BB members who have had children escape and often they have posted about how awful it was.
If that person posted to say "OMG someone reported me to DOCS because....." I would probably say that I get that it's embarrassing and horrible but that the person who reported them acted out of compassion for their child.

And if the member wasn't searching frantically for their missing child my eyebrow would be raised just a little.

Personally the way my children scream like they're being killed if I make them do something against their will I'm totally expecting a visit from DOCS or the police one day.