When Andrew came back earlier, Luna actually noticed him. She only entered after he had already gotten dressed.

Andrew immediately made something up, "You got me… Back at Sword Lake near Swordhaven Keep, I ran into a skilled martial artist. We got into a fight over a disagreement, and in the end, I completely defeated them. Unfortunately, my clothes got torn apart in the battle."

Luna nodded slightly. "Tomorrow is Sheena's duel, and things are bound to get messy. So, Andrew, you should rest