If there are zombies in Portland, I'm more concerned with them eating me, not them leaving their car door open.

Good message to get out there. If your car door is open, you are inviting robbery. Your distracted counting money and not paying attention sorting your packages. Get in your car, lock the door and pay attention to your surroundings. Like I/A says, you also may cause someone to run into your door and get hurt.
Another thing, Children and animals in the car while you leave them alone for just a few minutes gets so much news. Just Stop it. No excuses, just Stop it.