The Hertz website makes it possible to book for next year, I made the same mistake once. My outcome in LAS was a bit different - they couldn't pull up my reservation, but were able to find me a walkup rate that was cheaper than what I had reserved, and had plenty of cars so I was on my way with no hassle at all.

IMHO Hertz should have a maximum 330 day booking window like the airlines do - it will prevent mistakes such as these. BTW - I didn't type in the next year, I think it was something funky with how the calendar function works. Now I am especially careful to check.

At least you enjoyed a Volvo. :-)