Wow, that is tough. I would say to write in a Google Doc or something like that, but that feels far less personal than a hand written journal. I have heard of some people making email addresses for their kids when they are young, then they email them and when they are 18 they give them access to the account. Who knows if email will be around in another 18 years though! That's too bad for your colleague. I can't imagine how devastating that must be.
It was the hand-written part that he was so connected with, at is rare to write that way these days. He is pretty upset about it today too, though we didn't talk about it directly. Instead, we had some fun chatting with colleagues :)
Yeah, that doesn't surprise me. I totally get that. Such a bummer for him...