Board Thread:Naruto Discussions/@comment-7292165-20140715160041/@comment-3279282-20140716094038

So we have:
 * Ichibi - assigned to Deidara
 * Nibi - assigned to either Hidan or Kakuzu
 * Sanbi - assigned to Sasori/Tobi
 * Yonbi - assigned to Kisame
 * Gobi - assigned to ???
 * Rokubi - assigned to ???
 * Nanabi - assigned to ???
 * Hachibi - assigned to ???
 * Kyubi - assigned to Itachi

The members we have missing are either Hidan or Kakuzu, Konan and Pain. I doubt that Zetsu would've been assigned one, since he's no fighter. That means we have one beast left. As I see it, it's next to impossible to tell who captured what beast.