IMO Forensic evidence in a vehicle might give all kinds of clues to the investigators. It may help in identifying a person (DNA) as well as a location, through vegetation samples , dust particles, air pollutants, insect remains, soil samples ... just to name a few of the obvious ones. A perp, either Dale here or someone else, has all the reasons in the world to keep his/hers exposure to a minimum if at all. We know the the H3 at some point must have been part of the crime seen, even more so if it was used to transport a body, we know there are "limited evidence", we know we possibly have a body that has been disposed of effectively, we know the police has not been able to charge anyone with anything directly connected to MP disappearance and from there IMO we must deduce (absent evidence to the contrary) that this was not an "on the fly" abduction by a perp who just kills then simply dumps a body, quite the contrary, this perp ties up loose ends quite efficiently, moreover IMO it is entirely possible he has done it before.