Also not a rant against the way things are. Fully recognize the majestic stupidity of my actions.
I feel your pain.
Any chance you ever started your arc over on the Test server, and there's some of it still there?
Ugh. I feel your pain -- I had a similar problem back when I was working on it in beta. I've long since turned AutoSave off and just started regularly saving my work as I go. It's easier and safer than relying on an autosaver that doesn't know what I'm truly up to or how best to archive it.
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Mission Architect Works: DIY Laser Moonbase (Dev Choice!), An Internship in the Fine Art of Revenge (2009 MA Award Winner!) and many more! Plus Brand New Arcs for Issue 21!
Yes, autosave, no like. It also seems that my worst can't get my cursor and text to the right place would happen when autosave kicked on.
Just thinking about this makes my eyes itch. I think I'm going to move an archival copy of my finished arcs to someplace safe.
Arc 55669 - Tales of the PPD: One Hell of a Deal (video trailer)
Arc 64511 - The Wrecking Ball
Arc 1745 - The Trouble With Trimbles
Arc 302901 - HappyCorpse
If you save something to a file name, autosave autosaves to the file name.
Don't rely on autosave to 'autosave' file name.
I turned off autosave after I saw the first save message pop-up. I think I'm too skittish of autosaves after playing Morrowind for so long (autosaving, or quicksaving, on the same save file would eventually corrupt it), so I shut that thing off immediately. 
I tend to manually save after any long-typing I had to do (like all the contact's dialogue, or a series of objectives/clues). <_<
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Peppermint Cat-- Lv50 Mewtant Ice/Eng Bls
I lost everything...
I was working on a single arc, and so was relying on autosave, I found this to be convenient because it meant all my saves were heading into the same file, and I would never have to check to see which was the more recent save.
Well tonight I clicked edit, and simultaneously alt-tabbed to check a reference, and somehow I had managed to open a new arc, and stayed out of frame long enough for auto-save to occur. I lost an almost complete five mission arc. It was truly some of the best work I've done so far and now I've got to start over.
Turn autosave off or Don't rely on it. Save everything over 9000 times in over 9000 ways. Get one of those time-machine programs that allows you to undelete. I feel so stupid I could cry.
And I appreciate any suggestions, but I'm not looking for ways to get it back, I can confirm it is G.O.N.E gone, I've got some pretty powerful lost data recovery software here, but it doesn't change the fact that I saved right over my only copy with a fresh storyarc file.
I just want to leave this as a public service announcement.