Ahh it’s okay! Like I said, I always love to have TG/Hide-related discussions/headcanons!
Hmm I have never thought about this tbh. All of my theories about Hide surviving has him having a hand in turning Kaneki into Haise, and even if he doesn’t, there’s still a matter of whether or not he’s still working with the CCG – and if he did, there’s no way he hasn’t heard about the Quinx.
But hey let’s say that he doesn’t; let’s say he somehow moves on and is now working in a different place because he decides to cut all ties from the things connecting him with Kaneki – I think he’d notice him. Hide’d spent most of his life being by Kaneki’s side I’m sure he can tell if Haise’s Kaneki, after all, this is the person who still managed to recognize Kaneki under the mask and blood and the new white hair and everything in a dimly lit sewer I don’t think he’d have trouble figuring Kaneki with a new hairstyle. He’d be surprised that for sure, and I guess it’ll be all kinds of awkward in their first meeting because Hide’s un-Hide-ly stumbling between words and disbelief and Haise being.. well, the usual unknowing Haise (”Why are you staring?”).
But seeing Hide’s tendency, I guess he’d notice that Kaneki has a new life now, and he looks quite happy too, so in the end he decides not to really interfere with Kaneki’s life. Also please note that I’m really basing this headcanon on a random encounter, like in the middle-of-the-street encounter. He does, however tries to find more information about his friend and what happened about him but that’s that. He might end up going back to his old part time job of supplying infos about ghouls to the CCG too, and pass Haise a few times (I imagine Hide’d still talk with Akira), but he never really try to connect with him. He’s content to know Kaneki’s alive and well even when he’s not part of it.
..tbh I was wondering about the possibility of Hide slipping up and mentioning ‘Kaneki’ and triggering the memory like what happened with Nishiki, but then again if Haise did end up in pain, it’d do nothing but deepens Hide’s guilt and in the end it’ll be the ‘You’re happy now. you should be better off without knowing me’ route all over again.