So, I'm plowing through The Secret Armory of General Knoxx and generally loving every minute of it. However I appear to have come across a problem. While hanging around the Sunken Sea I was killing some drifters and got jumped by one named Skyscraper. I killed him, picked up my loot, and went on my way. An hour or so later I get a quest which states that I must kill him. However, when I go back to where I found him before he now refuses to show up. Looking through various message boards it appears that if you kill him before getting the quest then he won't reappear.
 
Is this in fact correct? While I don't care too horribly much about the quest rewards or anything I'm concerned this will prevent me from getting the Completionist achievement for finishing all Armory quests. Does anyone have any info or run across this themselves?

If he isn't appearing, than it's probably true that you can't kill him twice.

While surfing some more links that showed up on Google I came across one on the official Borderlands forum. Apparently you have to save and exit the game entirely and then load back in. He'll reappear then. So, anyone that has this happen to him that's how you get him to reappear.