Sooo glad that you're both okay!
I'll just add another idea...check your equipment often! I used to have a small station wagon, so my guys were all seatbelted in the back seat...with blankets and towels spread all over...covering the connections to the car seatbelt. I took it for granted that they were snapped in and working okay.
Rip was about 6 months old, he put his muzzle out of the partly rolled down window in the back of the car (no electric windows...these you had to ROLL down manually---you youngsters won't remember that). He then put a paw up, and the window pushed down further...he stood up and stuck his upper body out, at the same time that I moved into the right lane. He fell out of the window!
I freaked out, stopped the car (and the person behind me stopped too!)...and found him dangling (quite happily) about 4" from the pavement. His seat belt had come unclipped (he'd chewed on it without my noticing) and had just caught on the car seatbelt...just in time to keep him from falling all of the way.
I made sure to double check the seatbelt parts after that...pulled them out from under the blankets and towels so I could see it all...
"I don't have any idea if my dogs respect me or not, but they're greedy and I have their stuff." -- Patty Ruzzo
"Dogs don't want to control people. They want to control their own lives." --John Bradshaw