Bad luck on the crash 300WSM, but glad you are OK. Where my folks live in Oxfordshire is a major accident blackspot and over the years there have been several serious accidents byt the house. One of the duties of the police is to ensure that the belongings of victim are taken care of and do not get pinched, and this would apply to firearms as well as any other items in the vehicle, along with the vehicle itself. They remain with the vehicle until it is safely recovered.
I would have thought the police would pick up the weapons and lock them inot the police car and hold them in safe custody until you were able to reclaim them.
Provided you have taken reasonable precautions to prevent them falling into the wrong hands that's as much as any of us can do.
This is one reason why the Police do like rifles to be carried with the bolt seperate to the rifle, thus if NED should pinch the rifle from boot of the car, it is useless - I lock the bolt inot the glove box, and like others do chain guns to the car so as to prevent casual theft.
But lets be honest, any cable takes just a few seconds with a pair of bolt croppers, and even a gun box / cabinet, doesn't take that long to open, or to rip out and carry off.
Any body who does pinch a weapon has committed a very serious offence - not only normal theft, but also is now in illegal possesion of a firearm.