Sam2,
The umdana has to have been evident at the time of the kabbola. It doesn’t work retroactively. Anything after the person comes out of the mikva is irrelevant, even if it is only 3 days.
If he had told his friends, before the kabala, that they were going to go out that night to Chipotle, that would be an umdina d’muchach.
Yekke2,
It’s not that Daas is not important, it is that we recognize the Daas he speaks out loud, not the purported Daas he has in his heart. The concept of dvarim sh’blev aynam dvarim always comes up with things that require Daas (like a kinyan), and af al pi ken, dvarim sh’blev aynam dvarim.
Those that claim you can retoractively annul geirus (not that I think this is correct) would probably argue that it is gilui milsa b’alma. What the Rambam is talking about is when the person has a genuine change of heart, not where he is suspecting of never being sincere in the first place.