While it may be sad that it isn't that way anymore, it's simply a fact of life. Like London, I never leave anything of value in a vehicle parked outside. Even the SAPD chief has stated if he could only get people to quite leaving valuables in their cars, and lock their doors, crime in this city would drop significantly.
However, knowing there was a weapon in the car would definitely change my approach to someone breaking into it. Luckily this turned out alright, it could have been much more worse...
I can agree that removing valuables from cars would probably reduce the loss, however, for most of us the damage to the car is a bigger cost than anything they may have stolen. I am getting really tired of people blaming the victim rather than the criminal. There is no security device that is 100%, so at best you are making crime take a few extra seconds/minutes.