When I first encountered Trooper Ashby and engaged in his dialogue, I noticed the special option that requires Inez. So I loaded up a save from before I engaged with Ashby, and progressed my quests along until I was able to get Ashby to join my crew. Shortly after doing so, I went back to talk to Ashby and he's nowhere to be found. I double checked the site where he blows himself up with a grenade, if given, and there's no body or ground damage there. Is there some sort of hidden trigger that makes him disappear if not engaged after a certain point/amount of time?

Same thing happened to me, he is just missing now