Locked Car

Len parks his car, locks the doors and goes off for a walk in the park. After some time he returns to his car and realizes that he has lost his keys while walking in the park.

"Damn," he thought, "I'll never find them." Then he smiled, realizing he had a spare set of keys in the glove compartment. Seconds later, Len is driving home without having forced his way into the car.

He didn't break a window or seek any other assistance. So how did he get into the locked car?