I suppose he knew in advance that he might do it, although he probably didn't want to. You'd have to clue in the Secret Service about such a possibility. I wonder if the players who did it were aware of Pence's presence, and decided to kneel as a way of sticking a finger in his eye. If so, what children. But they got a reaction, and I guess that's what they wanted:
I stand with @POTUS Trump, I stand with our soldiers, and I will always stand for our Flag and our National Anthem. pic.twitter.com/B0zP5M41MQ
The game also served as the Colts' day to honor Peyton Manning
The game also served as the Colts' day to honor Peyton Manning in a variety of ways, and Pence - who was Indiana governor during much of Manning's time with the Colts - would have understandably wanted to be there for that.
He was present for the Manning ceremonies, but he didn't stay long thereafter. And he didn't want anyone confused about why he left.
Good. Unsurprisingly, President Trump thought so too:
I asked @VP Pence to leave stadium if any players kneeled, disrespecting our country. I am proud of him and @SecondLady Karen.
As we've already established here, the anthem protests are perpetrating a total lie about America's police officers, and the kneelers deserve to be called to account for their slander. It wasn't long ago that we had a president who would have joined in slandering the police while hailing the kneelers as the greatest kind of Americans. It's nice to see that at least the White House is once again on the side of the good guys, and isn't going to pretend that every protest is honorable just because it's a protest.
Besides, from the looks of this game (6-6 at halftime), Pence isn't missing much anyway.
