What version of excel are you using?
If you are using xl2007, then I think that it creates a .tmp file to use to
indicate what user has the real file open. I don't think you'll find a real
..xls file in it.
If you're using xl2003 or earlier, then excel doesn't make any .tmp files
(except for some files in your windows temp folder that are used with controls
(on sheets and userforms).
But many antivirus programs will create files with that extension. I don't
think you'll find any excel file inside those either.
Just out of curiosity, how big is this .tmp file (in bytes or kb's)?