A machine that hosts a non-global zone can become unusable. However, if the storage that the zone lives on, such as a SAN, is still usable, it might still be possible to migrate the zone to a new host successfully. You can move 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 re-configured so the zonepath is visible on the new host. Since the zone was not properly detached, you will have to first create the zone on the new host using the zonecfg command. Once this has been done, attach the zone on the new host.
The procedure for this task is described in How to Migrate A Non-Global Zone Using ZFS Archives.