My main concern about leaving children in the car is more to do with fire than theft (it would take a very desperate thief to steal a car with kids in it.  I know of a girl in our local hospital who as a child was left with her sister in the car in a petrol station forecourt.  Her mother locked the doors (they were about 6 and 8 at the time) and for some reason the car suddenly went on fire but they were unable to be rescued because the doors were locked.  The older one sadly died but the younger one spent more than a year in hospital (she was literally burned to the bone) and has had over 100 skin grafts and reconstructive surgeries over twenty years.

Once, years ago I saw a mum pull up outside a shop and dash in leaving the baby strapped in the car with the engine running.  I waited by the car to “protect” the baby and gave her a complete mouthful when she came back…..........she’d been buying play dough…........!!!