A system that hosts a non-global zone can become unusable. However, if the zone is on shared storage that is still usable, you might still be able to migrate the zone to a new host successfully by moving the zonepath for the zone to the new host.
In some cases, such as a SAN, the zonepath data might not actually move. The SAN might simply be reconfigured so the zonepath is visible on the new host.
Since the unusable zone was not properly detached, you must first create the zone on the new host by using the zonecfg command. After the zone is created on the new host, you can attach the zone to the host.