Front Air Bag problems of the 2005 Audi S4

In August 2006 while driving my 2005 Audi S4 convertible on a busy street in bloomington, indiana at 45-50 mph, my car died without warning. . . I. E. No power steering, brakes. I was able to navigate it off-road and then towed to royal Audi in bloomington, in. They kept the car over a month thinking maybe I needed a new engine. However, eventually they said it was a fuse which was replaced and the car drove fine. However, driving cross-country in January 2007 while on i40 in west oklahoma, trying to pass an enormous truck, I found I had no brakes and rear-ended another similar large truck ,totaling my car. Despite a severe accident no airbags deployed either on the drivers or passenger's side.