Even if you own a Tesla, you should still carry your car keys at all times. Tesla owner, Las Vegas investor and entrepreneur Ryan Negri learned that the hard way as he got stranded with his Tesla six miles from home near Red Rock Canyon, Nevada. Negri used the Tesla mobile app to start the car at home, and didn't bring his keys; but when he had to stop and restart the car to adjust a dog seat, there was no cell service, so the start-with-phone method was useless.