I can only think of two possible reasons for the body to be placed where it was.
Killer in a big hurry to leave town (permanently) and found secluded spot (obvious cause other people dump there) and figured no one would see him do it.
Only other reason, what JJ said. TO make sure searchers COULD FIND the body. So the insurance claim could be paid.
-- or --
It was a spot that didn't have press or searchers crawling all over.
Besides, it was on my way home after putting out all those signs and passing out flyers ...