[Kaiba does go looking, as after finding some dry-enough wood and an ill-advised tree battle that he's happy no one actually saw him not win (it was a strategic withdrawal), he still had time to wait around long enough to get--not quite "worried," but perhaps "concerned," given his group's wildlife encounters the previous day. So he keeps quiet as he stalks through the forest, axe in hand, listening for breathing or footsteps or Something Worse. It's kind of anti-climactic when he finally comes across the waterfall and Yusuke looks all in one piece]

--What happened?