Nowadays it is not safe to leave a child alone in a car. In fact, you can be arrested for it.
No child should be left alone in a car. NO CHILD. NEVER.
Yep. We used to leave our car and house unlocked, too. When sent to the car, it was close to the restaurant and watched. Not out of sight in a mall lot or such. And I'm not talking about a toddler that would be fearful, but an older child choosing to misbehave who can appreciate that particular discipline of disassociation. You know, I'm finding I really crave nuanced adults.