My friend lives by himself and it's pretty quiet around the apartment. I know hs old roommate had a ferret, it's been gone around over 6 months now. Maybe that could be it. When he was at my house all he smelled was other cats and I think he was used to other cat smells since his former foster family had almost 20 foster cats in the house. He's moving into a new apartment in about a week, maybe he'll like the new place better.