I've had this happen to me too at some random hotel chain (not Hyatt). Stayed a night, ended up having to stay another night, and was asked to switch rooms when I made my new reservation. I think it is just one of those common customer service situations where it is likely possible for the agent to accommodate you, but either the automated system makes it difficult or it requires manager approval. I could think of a few other scenarios where it might be legitimate though. For instance, maybe a larger group requested rooms together and your room happened to be in that grouping. Anyways, I just enjoyed my fresh, new room lol.