Hey mate, I guarantee you the interviewer didn't think you blew it. Stuttering is not a bad thing and is something that makes you unique. Next time, I would advise that you disclose your stutter at the start of the interview, lets the interviewer know and also takes the pressure of your shoulders. A good company/workplace will never ever pass you off because of your stutter, and if they do, you shouldn't want to work there anyway. Best of luck with it mate, and see how you go next time. Remember to be positive and know that you are no less than anyone else because of your stutter