i hate that too!
But here we have a law,in the summer it is ILLEGAL to leave your child(under 13)and animals in the car,it gets soo hot here.You have your animals taken away if you get caught leaving your animals.You can also report them,like in your case you could've called the police and they would take their dog away.One i remember from last year,a lady got her German Shepherd puppy taken away,b/c she left it,while she was inside eating lunch

I wouldnt even dare leave my kids in the car