Obi-Wan might be lost in his own thoughts but that didn't mean he couldn't tell when Rob entered the room. For a telepath, a Jedi especially, a close friend or lover was like a beacon of light in the dark and it shook him out of his particular mood and put him in a different one entirely - panic.

Why didn't he think to cloak himself to keep anyone from noticing him? He could try to mind trick him but Obi-Wan didn't think that was really the right thing to do to one's lover.

"You can forget you ever saw me like this, right? I ran into the door. The one that flips everything around."