you do right mate too make a complaint and make sure you get something done about it, don't let the feckers get away with it, you should make sure you don't leave your new one there again, arrange with the farmer to leave something less value.
hope you get everything sorted out, and next time you see the cops again give them this
id definately make a complaint as it resulted in you having to drive home with an unsecured rifle in your car and if youd been pulled you can garantey theyd find some way of nicking you and taking your gun, their b*stards mate treat them as such. just an idea f