Who do you think was the first person ever to forget their car keys?

Probably the inventor. There's no way he remembered it for every test drive when it wasn't anyone's routine yet.

The Chrysler Corporation introduced the first car key that could start the engine when inserted into the ignition in 1949. Before this, car keys were used to control the electrical circuit and lock the vehicle's doors, but drivers still needed to use a crank handle to start the car.