This has happened to us on a couple occasions. Now, we make it a habit to walk through properties during our trips, so we can decide where we might want to stay in the future. So when we make the reservation, we can request the specific room or section. I also follow-up with an e-mail to the hotel just before we arrive, to confirm that we still have that room reserved. It also helps that we try to stay in small hotels where there aren't many room options so they can't pull a "swtich" and stick us in the crappy wing.