Looking at the maps and the photos of the area, is it a fair conclusion that anyone who hid a body in that area (long or short term) was either in a situation that they had not planned (would anyone actually choose in advance to use that area?) or just very stupid. The fact that SY are putting such resources there means that they think there is a reasonable chance of finding something (when balanced with the resources required). Therefore, SY have spent some time considering theories that involve someone hiding a body under a set of circumstances that they did not plan. This still, of course, could include a planned abduction that went wrong, burglary that went wrong as well as other options that have been discussed. To put it another way, if SY were absolutely convinced that the body was hidden/disposed of as part of a pre-planned schedule of events and executed by someone who was not very stupid, they would not be digging in this area.