From memory a lot of the newer Nissans don't even have a keyhole for the ignition, just a pushbutton.
Also if you're within range with the fob - someone can push the button on the doorhandle to unlock it, start the car, and drive off. And they can keep driving it until they shut it off.
I drove a car in the shop to put tires on it, pulled it out and parked it, another guy drove it in to do the alignment, then back out in the parking lot. All while the customer was sitting in the waiting room with the key fob in his pocket. The car was started 30ft away from him. And I saw my old landlord drive his Altima home and shut it off only to realize his key fob fell off the roof 30 miles away.
And to stay on topic, I'd be willing to bet you warped at least one of the heads in your car.