When I watched the film a few years ago (much after the year of it's release and Oscar win(s)), I remember being blown away by the film in particular, Casey Affleck's performance and the script. When I googled the Oscar results of that year, I remember being disappointed. And it's funny because both categories won the Oscars. At least one of them didn't make it and no, it wasn't being disappointed about the film not winning Best Picture because:
1) I was mostly focused on the acting performances, topmost Casey's and the intelligence of the script. The same reason why I didn't even focus on the direction though the director was a hell of a shot too to execute it all.
2) After a year or two, watching Casey Affleck's win and thinking wtf? I was clearly disappointed on not seeing him win. And fyi, that was the first time I saw him winning. Don't ask me whether I remember seeing some other "nominee" win it. I don't even remember who did.
So I think it was more about seeing Casey lose than the script losing out.
I'm hoping now, if this was truly a Mandela effect, to see Heath Ledger win for Brokeback Mountain (2005) but that would be impossible as I know it too clearly!