My position on leaving a child in a car ---- never do it!
I would not leave $1,000,000 in my car unattended, so why would I leave my daughter? If she falls asleep in the car, I pull into the garage and leave her in the car with the windows rolled down, the garage locked up and the door into the house wide open so I can hear her when she wants to get out.
She knows I don't leave her in the car because sometimes she has requested to stay in the car and I've answered, "Mommy doesn't want someone to take you baby, come on, get out." So when my ex left my 4 year old in the car, buckled in her car seat and he ran into his apartment to get something, she was madder than a wet hen and still has not forgotten it!