Anti-theft Devices problems of the 2015 Chevrolet Silverado 1500

While using a spare key to my 2015 silverado for the entire day, and driving over 70 miles, the "anti-theft" warning light suddenly came on. I continued to drive approx. 10 miles with the light on and while turning off a busy road, across on-coming traffic, the truck completely shut off. No steering, no forward movement, nothing. It virtually went dead! I was able to put the truck in park and try to start it again (thank goodness no traffic coming through at the time). After several attempts it started again and I began to drive around the corner to my home, where it completely shut off again, in front of my driveway. Had it towed, as I was nervous about driving it again. The chevy dealership service department was unable to conclude what happened. They tested it with the spare key, and still no sign of any trouble. I am reluctant to drive this truck.