It's extremely misleading. It's every time parents call the cops because they can't find their kid. Many are resolved within hours. Almost all are resolved peacefully. If your kid is a habitual runaway each time you report they didn't go to school or come home counts as one. After kids being assholes the number 2 cause is non-custodial parents.

About 1 in 10,000 aren't found or found alive. So 50 or 60 kids out of 84M that are under 18 at any given time are grabbed by predators or die whilst running away (hint OD)

Half a million kids go missing?

If I remember correctly it’s mostly kids that runaway get reported as missing and then are found within a day. Or it’s when one parent kidnaps the child. Basically custody battle stuff.

A small number is actual kidnapping by strangers or trafficking.

Its seems weird because its probably made up, its the common rule of the internet - not everything is true.

Edit: The lower bound is actually true for the USA, see other comments for explanation.