You, obviously, caught Scott on an off night. Who knows what happened after the show. Maybe he had a headache, maybe he was tired, maybe he was just missing his kids. It's ridiculously unlike Scott to refuse to do autographs.
Dana Dufine personally came over and told you that "Scott doesn't do autographs?"
I don't think you talked to his manager at all. My guess is you were told to go away by a roadie or someone working for the venue.
I've met Scott a number of times, and he was always pleased and willing to sign absolutely anything at all. Not only that, but he was willing to stay to make sure EVERYONE got their pictures and autographs - he left no one out.
On top of that, I have his signature on everything from CD inserts to fan-drawn photos thrown on stage to a scrap of paper he ripped out of a notebook. He's certainly not fussy about WHAT he signs.
As far as "not liking large crowds" - I've seen as many as 20 or 30 people backstage before, and he was happy to talk to and sign for all of them.
Please don't take any offense to this, because I certainly don't mean any - but were you guys yelling or shouting at him? If the crowd was being obnoxious, you may have scared him.
Regardless, I am sorry for your misfortune after the show. Try your luck next time - honest to goodness, I've never heard of him refusing an autograph. He's usually a very friendly person.