[Armin's voice is very careful, like he is taking great care to pick his words.]

Perhaps. His pokemon may also have gone to other people, even ones he might not have known so well. It might be worth checking that out too. You did mention there were several people of your team here, right. Maybe they...

[He lets it trail off there. He's certain Shiro can fill in the blanks. And if this Keith guy is gone, maybe at least having his pokemon around is a comfort.]