Sex trafficking of minors redux, how did the captors pull it off so long?

This article said that major child sex/pornography rings were broken up in about 30 countries. It did not say if the 200 or so children saved were held Jaycee Dugard style, hidden away out of sight, fed gruel and chained to a radiator, etc., but for the sake of argument, let’s say they were. If they were kidnapped off the street or wherever, were their captors so good as to not have any sightings of these kids which had to be reported missing by their parents? In the third world you hear stories of parents selling their children to wealthy people, brothels, factories and such, to settle debt, make money or eliminate an extra mouth to feed, but in industrial nations you would not likely find this. Were all these kids saved from third world nations, exported to industrial nations like some ”sex biscuits”, cargo, or something? If there were children from industrialized nations and they were not plucked off the corner waiting for a school bus, where were the parents? If the minors are being utilized are in an industrialized nation and not held captive how did the adults gain access to the little nippers as to exploit them? Did the parent not notice little Billy or Brenda’s new friends, be they adult men or women, that would take them away for hours and had them coming back all tired and maybe rough around the edges? If the parents were not as keen in seeing any tale-tale signs, or clueless not to notice, were they in on the take, being paid off not to not notice or look too hard? If the child is held as a prisoner, do they never get broken bones, or get chronic colds or illnesses needing the attention of a doctor? It would seem very hard to completely hide a child without any sightings at all, even Jaycee Dugard was seen sporadically, even if it was either by people who did not think anything of it, or the authorities never followed up if anyone did notice.