[Chip]

I've had a similar problem: I've been outside, with my camera in my bag, and within 5 seconds after taking the camera out, the lens fogged up.

I think it has to do with the lens being sudenly placed in a more humid (or just different) environment. In your hotel rooom, the AC likely did a great job dehumidifying the room, and my camera bad was likely less humid than the outside air.

But after a few minutes, the lens should adjust to the new environment and the fogginess should go away.

Only way I know of to prevent this is, for at least a few minutes before you need to take a photo, have the lens in as close to the same environment as it will be when you're taking the photos.

I don't know of a way to get the fog off once it starts condensing on the lens. Patience is my only solution.