i wanted to ask:

Because she wasn't in her office, she was in court questioning Mary Cattermole.

I think the eye just worked like a peep hole to see who was standing behind the door.

When Moody used the eye, it was almost always in his eye socket. I think I can remember only one occasion where he pulled it out and still used it.

I think Umbridge used the eye almost as a CCTV camera. When she returned to her office, she'd view what it'd seen in her absence, possibly by touching it or lifting it to her face. She couldn't see what it saw while she was on another level.