Hi there,
I don't think that's a bad sign in itself. Where you able to finish the case? Including recommendation?
After the case, the last part is typically you asking questions. Did you get to do that? And how did the interview actually end?
Usually interviewers are told to not finish early, but there could be exceptions (e.g., when the candidate wants to finish early or when something truly urgent happens with the interviewer).
Ariadna