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I'm also a post-apocalyptic story fan, and have read most of the books mentioned.
I was trying a search for the OP's book, and came across this site that has tons of listings for online post-apoc books and stories, as well as some that have been published, and think you might want to browse it and see if you find your book: Online Post Apocalyptic and Dystopian Fiction
In the meantime, I've been sidetracked by one of the books listed, "Deep Winter," which is available online, so have stopped my search for now. Hope the link helps.
Oh, and just in case "Panic in the Year Zero" is the movie Mac is talking about, here is the full movie on YouTube: