Right, in this case the scientists have a general plan of where the monitoring
sites will be (based on the geology

and other information we have beforehand) and will have in
some cases the route traveled if there is a road or trail etc. between sites.

However, as someone travels, the search area goes up by
a huge factor based on the distance they could travel in
the time since the point last seen. If all you have
is a note at home, you could be looking at a "bastard search"
(where the the lost person is somewhere in a bar or brothel
instead of that class 3 peak.)and the searchers will have
to waste time checking out the "Owl Club".

If you know the point last seen and the time,
you can deduce the probability the person is in a certain
area and then based on the search methods, the probability
that the person will be discovered.

Frequent check ins before you are a victim, really speed the SAR effort up.