2017 Premier died on freeway during test drive - lemon or a real problem?

Hello everyone, new here. I was hoping this would be a positive post about a great car I was going to buy, but now am not so sure. I went yesterday for a test drive of a 2017 Premier, primarily to see how it drove on the freeway for part of my commute (especially the hilly parts). It did great on the uphill drive (without using the hill mode) but on the return, downhill trip, after driving a total of 10 miles, we heard a warning chime, immediately followed by motor power cutting off, a yellow check engine light coming on and the now, as I have learned, the infamous "shift to park" message appearing. As we were going downhill, we continued to coast slower and slower and the power steering seemed to be off (as was A/C, though the windows worked). The salesman said he had never seen this happen before but not to worry, the car would go into "turtle" mode and I would be able to drive but only at 15mph. Unfortunately, that never happened. I was able to coast off the freeway at the next exit (1/2 mile from the dealer) and pull to the side. We could not turn off the car with the power button, it simply kept recycling to initializing, but nothing ever happened. We even walked a ways away and came back, but could not start the car (or get it out of park). It was a pretty scary experience and is making me question whether to buy a Volt since I wonder, if I had been going uphill when this happened, could I have gotten over to the emergency land in time + avoided getting hit in fast rush hour traffic. I know that forum posters sometimes tend to extremes, love it or hate it and post all problems, making it difficult to judge just how common a problem really is. So, I would appreciate any feedback on whether I had a lemon or whether this is a significant enough issue to wait (i.e., 2018 model year) to hope it is recognized or fixed. Thanks for any response. Really did like the Volt otherwise.