Can't start Task: Augmentation Crafting because Krogan Engineer is not appearing

I can't seem to start the mission "Task: Augmentation Crafting" on Elaaden because the character who starts the quest, Krogan Engineer, can't be found.  I've read other people having this same issue.  They say that he was appearing when you first arrive on the planet but after progressing and completing quests on the planet, he doesn't seem to be appearing.  Can anyone suggest anything to try in order to get this mission started?  I'm trying to complete all the missions (and there are a ton of them) and it would really suck if I couldn't get them all because of this one.  Any help would be greatly appreciated...