[Nagito dusts himself off a little, speaking matter-of-factly as he does so.]

There was another alcove like this that had evidence of other travelers. Some of the items left were fairly valuable like food rations and even what looked like some sort of playback device. It's unlikely that things like that would have been left behind unless the situation was pretty extreme, meaning that whoever left them was either found or killed.

[Despite his odd personality he's actually quite smart and observant; there's a reason he was able to solve five murders before anyone else and orchestrate an essentially unsolvable crime. And more.]