Disk Utility won't mount a disk
I have a 1TB HDD that was in a backup system that I'm sending in to the vendor for replacement. I am trying to mount it in an external enclosure but DU won't recognize it. When I first plugged it in, DU mounted it fine (it was 1TB of a 2TB sparse bundle) and I did a simple erase. When I swapped it out for the other HDD and then swapped it back, DU will no longer mount it. In fact, DU doesn't show a darn thing except the expected boot volume. I've disconnected, reconnected, powered it off then on, but nothing happens.
I'm on 10.8.2 using Disk Utility version 13 (444) on a late 2012 Mac mini.
Is there a way of "forcing" it to mount? Is there a CLI in Terminal that will mount it? Is there a 3rd party app that will do this (it's been ages since I last used something like Disk Warrior!)?
I really need to do a secure erase before sending it back.
Thanks!
-Tod
Mac mini, OS X Mountain Lion (10.8.2), 10GB SDRAM 240GB SSD & 500GB HDD