My nephew once fell asleep in the car after about three hours of being extremely agitated, crying, thrashing about, etc. So we got home and didn't want to wake him. We (my mom and I) were so freaked out at the idea of forgetting him we just parked in the driveway, rolled down the windows, and sat on the lawn until he woke up. And even then we'd still get up every so often to check even though we could see him. At the time we laughed at ourselves for being so cautious but now, looking back? I think we were right to be hyper-vigilant. This happens too often and tragedy strikes SO quickly.