Slip of tongue in my Kellogg interview!

Not an issue. Do not worry about it.
I don't think it is end of the world and good for them perhaps to hear they have some competition

P.S. Most interviewers don't care about the details really (I recently talked to one one of the alums and they complained about how the people they were interviewing kept going and going about their work and projects that were irrelevant). I am not saying your interviewer was not listening - seems the opposite but they get overburdened with information and filter most of it out and may not have even heard or cared enough to put this into the notes.

For the interview process, someone else will read the notes most likely to make the judgement call on your candidacy so that Wharton slip will never be known