Originally Posted by Xina_LA

Same problem. If you log out or DC while doing the Showdown on Iokath // Get To Malcom mission, you lose the walker, there's no way to get it back, and the mobs will just cut you down on foot.

However, when I QT'ed back to the command spire and tried to walk through an instance door, the Mission Log for the quest popped up with a Launch button again. When I pressed this, I got the walker back. Give that a try.