If by “missing kids” you mean all children then of course YABU because children is such a wide sore trim that even say, a thirteen year old who disappears is considered a missing child. And in most instances those go missing of their own accord.
In terms of e.g. toddlers etc, iirc 97% of thos who disappear turn out to have been harmed by someone close to them. In other cases they are believed to have been murdered within 48 hours.
And as a PP said, those who have been found years later have been kept alive for far more sinister reasons.
I suspect in the situation currently in the news this story will disappear again as quickly as it turned up.
Usually in these kind of missing cases there’s a report every few years saying that there’s been a possible sighting or a suspect and then nothing ever comes of it. I remember the Ben Needham case, there were always reports from time to a time of a child who could have matched Ben’s description turning up somewhere, and then turning out to be just a random child. It’s only recently that it has been confirmed that Ben was likely killed accidentally and buried.
Also in high profile cases, if they are never solved, it’s not that uncommon for someone to come up at the time that person would have been an adult to claim they are in fact said person, for no other reason than money usually
There will almost certainly be people coming forward in the future claiming they are in fact MMC.