What time did you reserve your car? Was it before your flight was scheduled to arrive? Inputting your flight number helps on the not being charged for your rental should your flight get cancelled but it won't hold your reservation in their system should your selected pick up time be too off from your flight time. From your scenario it sounds like you input a pick up time for before your flight even departed, it's not common to receive a car assigning and parking spot before your flight has even left. In all the years that my husband has had
Avis Preferred it's never happened.