Only if you rely on only the app for unlocking. Whether you think it sounds unlikely or not, it's documented and people have run into this before with the S/X when data was unavailable.
You should always keep the fob or keycard around for safety.
All Tesla's come with either a fob or an NFC keycard. Owners are recommended by the car/manual to always keep them available.
But the convenience of just walking up to your car and it unlocking with your phone is enough for many people to take it for granted, and forget those other entry methods at home.
Most of us are more and more dependent on our phones for more and more things.
I know I'm often pretty sloppy about having backup printed information when I'm traveling for example. And, while I do still carry a (small) wallet (really just a business card holder), even that is becoming increasingly anachronistic. Also maps while hiking, etc.