(I ended up solving this, see my self-answer.)
I was typing in a Microsoft Word 2011 document on Mac OS X 10.8.2 that was originally four pages,
and saving every one or two pages, for at least fifteen pages. Then it started refusing to put
in page breaks, instead putting in two new lines and centering the cursor, so I saved again,
closed the file, and reopened it. When I did that, it only had the four pages that I started with.
I already tried "open recent" and searching in spotlight and finder for
autorecovery saves and for phrases that I had put in the document;
is there anything else I can try to get the rest of the document back?