I doubt it's in-game. As I recall, the first time it appeared was in one of the early trailers, before Cullen was confirmed as being in Inquisition. Then we saw it again when he was revealed. I think that was its last appearance, but I could be wrong.
Yeah, I guess they were just trying to 'hide' that it was Cullen? Sort of seems like sitting out in the open, covering your eyes with your hands to 'hide' during hide-and-seek, doesn't it? I think it did make an appearance or two after he was confirmed, though, because he's wearing it in 'The Enemy of Thedas' trailer half the time. If I recall correctly, that was the first time we heard him speak in a trailer, though I can't remember when he was officially confirmed as being in the game.
That's not the only thing they seem to have done to Cullen's wardrobe for 'fun/speculation' purposes though. In one of the twitchstreams, he was wearing a--I don't know the word for it, so I apologise for that--'templar skirt thing' that matched his 'cloak/sash-thing' with the sword of mercy in crimson/god and I haven't heard anything about that or figured out how to get it to pop up in my game yet either.