My wife and I test drove a new Tahoe in January 2019 with push button start, dealer had started vehicle and we went on our usual test loop. It was snowing heavy and I stopped several miles out of town so she could drive it back to see how it handled. I pulled over and put the vehicle in park, when I went to get out the vehicle shut off. Threw me off at first, I didn't know what was going on. We've had a couple push button start vehicles so I asked my wife it she had the fob or saw it, nope. We searched for a brief moment and realized it wasn't in the vehicle. Shoot, here we are not pulled off the road completely and in a snowstorm. Now realize all of this is happening in less than a minute after the vehicle shut off, she is starting to call the dealership when I figure what the heck, I'll give it a try to start it. Push the brake and push the button, it starts!! Surprised as all get out we make our way back to the dealership. Who should we meet when pulling into the lot but our salesman coming out the door. He had just realized he had the fob in his pocket and was getting ready to call us. I told him what happened and he informed me that when we put it in park without the fob on us or in the vehicle it shuts itself off but there is a small window of time to restart it without the fob present which we accomplished. I'm not looking to try this out on different vehicles but that was our experience with a 2019 Chevrolet Tahoe Premiere, not sure if other vehicles operate in the same way.