Autosave: How to recover a lost document?

I have had this problem SEVERAL times during the last week:

I scan large PDF documents (300+ pages), and sometimes, just when I want to save the document, Acrobat X (10.1.2) hangs. There is nothing that I can do but to end-task (force-quit) Acrobat.

Acrobat warns me that I will loose my unsaved changes, but I have no choice but to force-quit. (I believe that it may be the scanner driver, not Acrobat itself, that hangs, but the scanner driver is not listed as an application in the windows task manager, thus I cannot force-quit the scanner driver, only Acrobat)

When I restart Acrobat X, or when I open the .pdf file in question, Acrobat does NOT ask me whether to open the AutoSave file.

This is corroborated by this unanswered post:

          http://acrobatusers.com/forum/pdf-creation/autosave-not-working-create-pdf-scanner/

I have located the temp file that Acrobat creates. For XP Professional SP3 it is located at the hidden directory

\user\Local Settings\Temp

In my case it is called A9R1F2.tmp, it is about 508MB for a 480-page document, the modification date of this file is within minutes of the Acrobat hang.

When I attempt to open this file with Acrobat, it tells me that the file is corrupted. If I change the extension to pdf, it tells me it is corrupted.

Now, after my automatic scanner has spend several hours to scan the file, my computer has spend several hours to do OCR on 480 pages, now that I have 508MB of data on my hard disk, how do I make Acrobat take this tmp file and make it usable?