Hello @Jane653,
Hosts and guests can't initiate the review process. Airbnb sends the request to review at various times on the day of checkout.
The only way to leave a review is by responding to the review notification or clicking / tapping the red review button in the review notification email. Airbnb sends the notification and the email at various times. Usually it's later on the day of checkout but I, as a host, have sometimes received them before the guest had checked out.
That variation is why you received the review before you reached your car but haven't yet received the notification to leave a review for your guest.
Steve.