I have raised five ten month olds. They almost universally fall asleep in a car and they are very quiet when sleeping.
If you are not normally transporting a child in the car and that child falls asleep. They could be overlooked once someone reaches their destination.
I'm sorry but there is NO WAY I would overlook something like that.
After a few minutes in the house, I’d notice.
When I would wake up from a nap or some other event and noticed there was silence, my kid’s location would instantly be queried.
There has never been a time that I had one or more of my children in the car and I constantly checked my rear view mirror to see how they were doing. The baby was always in a car seat in the middle of the back seat, so was more easily visible. I always knew exactly how many of my children were with me in the car. Never came close to forgetting one of them.