Real simple, if you have a wreck have the car towed to your house. After the wrecker leaves destroy the box.
That's the problem. The fact that it had to be there to operate the car, but is now after accident gone missing, means you are even more suspected, and may be charged with an additional crime of evidence tampering.
if you are in an accident that involves personal injury to another party (fake whiplash aside) - your car is going to be impounded.