He's clearly having difficulty talking about what happened. Joan wishes she was there, so she could see his face, hold his hand, rub his back, help make it easier for him to open up. If she wanted the details for investigative purposes, she would ask Sherlock. This is for Ted's sake. She thinks it's important for him to talk, to not hold it inside.

"It must have been hard to face him again," she says softly. "How did you feel when you saw him?"