For those interested in the "Frog Boys" case, I've found a short yet informative blog post from someone (apparently a British ex-pat teaching English) who lives in the area:
For those unfamiliar with the case, five young friends, aged 9 to 13, disappeared while hunting salamander eggs in March of 1991. This was a HUGE story at the time, and prompted massive publicity campaigns to get the boys' faces before the public, on the not-unreasonable assumption that they might still be alive. If you do an image search for 'frog boys', among the most common artifacts of the case are phone cards with they boys' pictures on them, apparently the Korean equivalent of milk carton pictures. The other, concurrent, response was to initiate massive searches of the area in which they disappeared. Some sources estimate that up to a quarter million people took part in one or another of these searches. That made it all the more surprising when, eleven years later, the bodies of the boys were found in an area that had been heavily searched.
Most of the articles in western media that I've read about this case make it sound as though the bodies were found lying on the ground, in plain sight, perhaps having just been placed there. From the pictures in this fellow's blog post, it's obvious that they had been shallowly buried, and then the ground eroded to expose them.
He posts several pictures of the bodies being recovered (nothing horribly gruesome - they're basically skeletons), which makes it plain that they'd apparently lain there for some time. He also reports that at least one skull had moss growing inside, reinforcing the idea that it had been partially exposed for months, if not years.
Bizarrely, the police would initially claim that the boys died of exposure. The bullet hole in the one boy's skull is very plain to see, plus the other skulls apparently bore evidence of the victims having been beaten about the head.
The bodies were found in an area that had been searched, repeatedly, in the aftermath of their disappearance. Were they buried there the entire time? That seems hard to credit, but then again, given that the police force saw nothing in the evidence of blunt trauma and bullet wounds to indicate foul play, maybe no-one saw anything suspicious about a freshly-dug patch of ground where people had gone missing. Looking for something like that seems basic common sense to me, but maybe there's some sort of cultural factor shaping expectations here.
At any rate, it remains an interesting case, although perhaps not quite so mysterious as it seemed from the accounts taken from western media.