Oh, you're right, I completely forgot that after the whole Chain of Memories events, the Journal was left completely blank, save for the message "Thank Namine"...
I think I understand how the Journal worked now. That would mean, Repliku is gone forever..
(still, in this series, ANYTHING can happen and he might be reborn or something, though I doubt that...)
That, and the events of Chain of Memories itself were never properly recorded in the journal, so there is nothing to digitalize.
In Re: Coded Jiminy also explicitly speaks about only two volumes of the journals, detailing the events of KH 1 and 2 respectively.
It depends on what happened to Repliku's heart in the end, but yes, with our current level of information from
both the games and supplementary material (Ultimanias and creator-interviews), Repliku is a goner.
Yeah I hate to think that Riku Replica actually being dead. I mean we've all seen characters "die" in the series to later be brought to life or in the RoD, but Riku Replica just died. The only thing I can think of is maybe like how Xion was made from Sora's memories and returned to him. Riku replica is made of data and Namine did tinker with his memories. So maybe he goes back to Namine somehow...? I'm not sure...
Which characters exactly did we see "die" throughout the series?
Of original characters the only examples coming to mind are indeed the Repliku and (possibly) Eraqus.
However, as stated in the Secret Ansem Reports of KH 2, "death" is something that happens when the soul and body get separated/the soul runs out of energy, resulting in the end of one's physical existence.
The heart however is unaffected by this and their ultimate destination seems to go back to Kingdom Hearts and sleep there forever, as the games are vague about this however this is just speculation/fan interpretation.
Some hearts are elsewhere though (like Roxas, Xion and Ventus inside Sora's heart, Eraqus in Terra's and Naminé's in Kairi's), and thus if they can be awakened again and given a new physical vessel (except Ven, he already has a body to return to), they can return.
Knowing this leads to the statement from above regarding the whereabouts of Repliku's heart.
If there is
any chance for Repliku's return at all, it would be needed to locate and then wake up his heart before giving him a new physical vessel.
Since no one knows where it is though, it might be like searching a needle in a haystack and give the question if such a great effort would be worth it.
He followed Xehanort because he wanted to escape his suffering by becoming the X-blade... That didn't work, so I wonder how Vanitas will act in the future... He must come back in KH3, he already did in DDD ; A ;