First, really sorry for your loss. Understand it is just property. I had my 20D stolen along with the $700 efs lens with it! I also slammed my trunk on my f1.4 50mm. Not so bad: $147 repair. It's gonna happen, you're gonna feel like crap and think of its replacement cost as just burning money.
You should check out the Professional photographers of America. They are a business and education centric trade org for photographers. Part of it's $100 annual membership is a $15,000 insurance policy for your gear...
Second: I've notice that with the new 24-70, if you don't lock the lens when mounting, you could accidently just be rotating the zoom dial instead of the lens itself. Without the lens fully mounted, it could still feel solidly on their until you move it just right and it can fall off.
Examine that in your lens swaps. Make sure it's locked and you hear a click!