"If I knew that, I would tell you," the Doctor said, words clipped. "Or I've been kidnapped. Again. Although I can say usually I'm in my body when I'm getting kidnapped."

There aren't many people who can get in and out of the TARDIS, especially not after what the Master did to it - between that, what he tried with River Song and what happened back in that ravine, the Doctor wasn't too inclined to give the man as much leeway as before despite whatever centuries worth of history they had. He managed to clamp down on any excess memories from leaking (too much) out. River might be his future wife, but that didn't mean that he felt comfortable sharing all the dark corners of his lives with the woman.

He turned her body back toward a shortcut back to the console room, lifting her foot when he noticed there was a...petal underfoot? That hadn't been there before. He moved to bend down like he would normally, a kind of sudden half-falling motion that worked when you had a body like his and finding that he couldn't quite do it the same way in River's. River's arms pinwheeled out as they tried to catch hold of something.