The new game update with The Grand Cast made it pretty clear that Terence actually accomplished the mission Dion sent him on to save the healer, however, I always play it that Dion assumed he did not after Origin rose from beneath Twinside not long after he tasked the man with going there.

It would be really easy to tweak a post-canon au where their Eikons are intact to also include he didn't, and while that's a lot of grief, it's also the makings of something awesomely slow-burn, seeing as Dion fully intended not to come back either way.