[He blinks at Yosuke in surprise for a few seconds. Then glances back to the wall in confusion. Then he shakes his head.]

I was watching the.... the wall. But now the thing is gone.

[He spends a moment contemplating this new devlopement, then nods.]

I bet it left 'cause the wall got all ripply. Hee~ ripply...

[He giggles, as though that's funny.]