I'm sorry for your loss - but I'm glad they're where they're needed. That's what I had to remind myself, when my best friend disappeared - that he's needed back home more than he's needed here.

[In other words, their world needs him more than Armin does, no matter how much it hurts Armin to admit it - how much it hurts him to be without him.

As far as them being left in the last jaunt - really, they have no evidence that they weren't, except that nobody has yet experienced it and returned to tell about it. Slim evidence, but it's the best they have, and if it's comforting to some people... Armin won't rob them of that.]