My guess is: Probably, in theory, yes. Ask a mod/admin to delete your post/thread after the 12-hour window, and if they deem your request needful and appropriate, I'm guessing it's within their power to do it. However, I'll bet posts/threads older than 12 hours will only be deleted under extreme circumstances (circumstances which may have nothing to do with whether the mods/admins were asked). Serrriously unlikely, is what I'm getting at.
That's totally guesswork on my part and I am not at all an expert in such matters. But it might explain why the thread you were following disappeared despite the 12-hour window rule. For further info/correction of any misinformation on my part, I'll defer to the mods/admins who'll hopefully post here and let you know.
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