It teleported away somewhere in an earlier chapter when Kakashi tried to use Kamui on it, right?
It's probably within Tobi's time-space dimension.
ofcourse it is, the main goal of naruto and kakashi/gai/killer b was to destroy the gedo mazo whilst it was transforming and kishi ended it up instead of naruto trying to destroy the gedo mazo who's about to transform into the progenitor of all things he made naruto go after tobi's mask and forgot about gedo mazoits behind hachibi