Disappointing the interviewer who invited me to final round?

I had an on-campus interview with a senior person at a company and I saw him again in the on-site interview room during final round. I didn't expect him to be there but he was sitting with 5 other people and I can tell from the look on his face that he was disappointed that he had invited me to the final round. I admit that I should've been better prepared and gave better answers. During the end of the interview, I was also prepared to use the same questions that I used before, but I had to bullshit some questions since he would remember them. Has anyone experienced something similar before?