Just happened to me this morning at the gas station. When I got back in the car and tried to start, got the key not found message and then the alarm went off which I was able to silence with the key fob. I remembered that there was an alternate way to start the car and looked in the manual which describes sliding the fob into the slot in the consol. But does not tell you where the slot is and if you read the description you can't tell which way you are supposed to insert it. But didn't matter because when I found the slot, it didn't work. I called my dealer. They were pretty useless as they kept telling me to look for a space under the steering wheel as it sounds like they have changed where to insert the fob in the 2013 models. Finally, I called my wife who brought the other key fob from home and that started immediately. I was guessing that the key fob battery was bad until I found this thread. Now, I'm not so sure. If it happens again, I will remember the lock, wait suggestion. Maybe good old keys weren't such a bad idea after all.
Stuart