The statically odds would be much higher than abduction from the property.
Hmm, this piqued my interest, so I had a look at some child abduction stats...
The USA's NISMART studies seem to have the most data that I can find. The NISMART-2 appears to be the most comprehensive cycle available - which estimates that of all "caretaker missing" episodes (about 1.3 million annually), roughly 9% involved family abductions and 3% nonfamily abductions—for a total of ~12% human agency cases. (Note: These are episode based estimates, not just police reports, so they capture unreported cases too.)
Family abductions (the bulk of the 12%) disproportionately affect kids under 6, who made up 44% of victims despite being only ~11-12% of all missing children overall. Nonfamily cases skew older (mostly teens), but the very young tilt the overall abduction rate upward in that demographic.
For unresolved cases after weeks/months... Most missing episodes resolve quickly (e.g. 46% of family abductions last <1 week, and ~99% of all runaways return within a year), so abductions loom larger in the lingering pool - 21% of family abductions go a month+, with 6% still unresolved at survey time, versus near zero for benign "lost / injured" cases. Among long-term recoveries (6+ months), runaways are 97%, meaning the remaining ~3% (abductions, etc.) represent a much higher abduction proportion than the overall 12%.
Sources:
NISMART Overview (PDF)
NISMART Highlights Bulletin (PDF)
NISMART Family Abductions Report (PDF)
NCMEC Long-Term Missing Analysis (Webpage)
Caretaker missing episodes = the caretaker did not know where the child was, became alarmed for at least an hour, and looked for the child.
These are interesting stats, but not 100% relevant in this case. If anyone else has previously done any research into stats that would fit this case, I'd love to hear it, I just don't have the time to go through it all.
As for the odds of "
him coming upon a mineshaft hole 5.5 to 12 kilometers away from the homestead in any direction on a property so vast" as per
@statt#1, I'm not smart enough for that, I think we'd need to call in the big guns, like
@Total_C
But, I do think that sounds highly unlikely, UNLESS - unless he had previously been to the mineshaft with one of his family members, and become curious about it from that, which would make sense as he might remember how to get to it. However, I would think in that case, this hypothetical mineshaft would have been brought up by the family to police in the beginning. IMO.