There's a good reason there are nine disguise buttons. I think he started to realize what was happening just before, as he started turning, but switching to a Pyro gave me the advantage I needed.
Hopefully this can serve as a lesson for a lot of Spies I see running around with just one disguise. Change your disguise when they spot you, it'll throw them off, or at least help.
Doktor Oktoberfest's is done, and should be up either tonight or early tomorrow - just fixing some typos.