beta
Seriously, even if he's desperate, he was clear enough to take into account it could all have been a dream or that he went back to his original timeline. As I see it, he has exactly 3 options:
1. It was all a dream and he woke up from it (highly unlikely, but from his perspective, it's the closest option)
2. The rift dropped him back to where he came from (unlikely in my book, because it's all too perfect, with how there's a completely plausible reason given for him to have dreamed and all)
3. Which is why I see a high possibility that he's hallucinating now, with what his brain made up to be the worst but most conclusive version of the scenario. Like, that someone is trying to break him by showing him what he would be most afraid of - that all of his accomplishments and the way for him to reach his dream had never existed. Doesn't have to be an illusion or hallucination, he could be trapped somewhere and shown this shit, but some sort of scenario along those lines.
Anyway, no matter which of these options you choose, it's impossible for anyone but him to have any memories of his alternate timeline. If it was a dream, then it never happened in reality. If he was brought back, then it never happened in that time. And if he's shown a deliberate world in which none of his accomplishments actually happened, they wouldn't let him have people who tell him he's right about what he knows.
What did he expect Daria to know, if he clearly never was her disciple in that timeline?