Thanks for your answer. My Temporary Internet Files folder is set to keep
history for 90 days. Unfortunately, the Excel files are not there.

"Bob I" wrote:

Probably in the Temporary Internet Files folder. You could ask in the
Vista group to get a better answer. Of course if you have security set
to delete temporary files when you close the browser, it won't survive
at all. So the correct method is ALWAYS do a Save As first, THEN do your
editing.

Gonzalo Martin wrote:

I downloaded an spreadsheet from Yahoo mail, opened it directly (instead of
saving it to disk before using it), worked with it, saved to disk (instead of
saving as...), closed Excel, and now I can't find the file anywhere. It does
not appear in Recent files, it is not found by Search even when including
hidden and system files.
In summary, there is no way to find where does Excel save files opened
directly from the Web.