Hi Holly,
Due to technical reasons, I don't think it's practical to go on waitlists for rentals without a base (fallback) reservation.
What you can do is wait a bit and ask again in another thread. One hint is that some reservations are cancelled on or around 31 days prior to check-in, so as that date approaches, you might ask someone to check availability for you.
Good luck!
Mark
Thanks for the info Mark!