"love to read forensics mystery novels... so my favorite author was Patricia Cornwell, not someone more "classic" like Hemingway."
There's nothing wrong with having someone like her as your favorite author. Heck, I inteview for Harvard and have loved most of her books. I love her plots and the fact that her main character is a pathologist. I also have enjoyed watching her main characters' personalities and motivations unfold over the course of her books.
What's important for students to realize is that an interview is a chance to be themselves, whoever they are. What caused you to stumble in the answer was your belief that the interviewer wanted you to say that some kind of classic author was your favorite. Instead, what the interviewer was interested in was you -- how you think, what you like, what your passions are.
From what you describe, I doubt that your interview tipped you in (which happens rarely as does the reverse). Your answers about music, however, may have verified what your recommendations and essay had indicated about your intellectual passions and ability to offer something to campus life.