Interestingly enough, I was in the area today and picked out that spot myself as I was driving by. It's heavily wooded and they could have easily tucked a vehicle in there without it being seen both from the road and from the Bosma house. There would be no view. In addition, the lane is so long that anyone on that property would not have seen the vehicle parked there in the dark unless they drove out the driveway.
This then brings me to other questions or thoughts.
DM, MS and TB head out on the test drive. They head out the driveway and turn left so they are travelling north up Trinity Road, and drive right past where the Yukon is parked (presumably). It seems to me that they would have driven back almost to TB's own driveway in his own truck, with TB deceased still in the truck, to pick up the Yukon. This could have been happening when the first seeds of concern started to unsettle SB. Just brutal.