Why wouldn't a car be crushed immediately? Here's one reason: all salvageable parts would normally be stripped from any salvaged vehicle before being crushed. It's the standard thing done at salvage yards, and it's part of how they make their $$, selling used parts to others. Could be that was the intent and SA didn't get around to it for whatever reason. Why take the license plate off a vehicle if you *want* the vehicle to be found? Why take the time to put tree branches, wooden posts, lean stuff up against a vehicle if your intent is that the vehicle be seen and found? To me those are things to try and quickly obscure a vehicle. Not very well, but somewhat.
Why disconnect the battery? Again, this is part of normal operation at a salvage yard. If a battery is still good, then it can be sold to someone else. Disconnecting it keeps the battery from being drained. It also means the car cannot be easily stolen by someone hotwiring it and driving away.
As for the key itself, if that key was really tucked way back in that nightstand and it slipped down between the gap in the back panel (there's a picture of this floating around where you can see there's a gap) then it's possible it was missed until someone really looked in depth and jostled that night stand. The question is: how thoroughly was that particular piece of furniture searched before? Was stuff just moved around a bit? People looked through some papers in there but didn't take every.single.thing off the shelves? I don't know, but a half-assed looksee is not outside the realm of possibility. As easy as it is to say someone planted the key, it's just as probable or even more so that whoever did prior searches just didn't do a thorough job of the searches.
The issue I have with the key being planted theory is: that there needs to be someone who 1. had that key and then 2. handed that key to Colburn or Lenk for them to be able to plant. Who is that person? Without that, how does the key get into the hands of police in order for them to plant it?