Here is some interesting information about the Zig Zag Trailhead, the supposed location where the vehicle was found:
http://nwhiker.com/MHNFHike32.html
Apparently the start of the Zig Zag Trail was moved from the Polallie Trailhead to its current location because of "mother nature". The Polallie Trailhead is just a little further up north on Highway 35 and appears to be a more widely-used and clearly-marked location with more parking space.
Map of Polallie Trailhead:
http://maps.google.com/maps?q=45.4175,-121.5701(Polallie_Trailhead)
Map of Zig Zag Trailhead:
http://maps.google.com/maps?q=45.4109,-121.5706(Zig_Zag_Trailhead)
Here are some things to consider: If you wanted to leave a vehicle at a location where it doesn't seem out of place, would you leave it at the less obvious Zig Zag Trailhead or the more obvious Polallie Trailhead just a little further up the highway? If you were Daryn or an abductor who was meeting someone, which location would make a better meeting spot? What does the choice of location say about the geographic knowledge of the persons involved and their familiarity with the area. How does the removal of the license plate relate to the choice, or the lack of choice, of the location? How does the vehicle being found out of gas relate to the choice of location?
Just some things I've been thinking about.