Excel file lost

Newbie here. I have an iMac, came with Lion. running 10.7.5. I'm running Microsoft Office for Mac 2011. I worked on an Excel file for a couple days, saving and closing. On the second day I opened the file, worked, saved, finished my work, then saved/closed. When I went to open today the file was not in the "Recent" list and I cannot find the most recent version. I checked the trash, it was not there. There is a very old version of the file with the same name but not the updated file. Any ideas about what happened to the updated file? No software updates since I started working on the file. Autosave was and is set to every 10 minutes.

Thank you for your help.

Autosave for MS Office 2011 is practically worthless and does not save a copy of the file once Office is closed. Unless you had chosen "Always make a backup" from Office Preferences, Save, your file may be gone for good.

Use Spotlight to search for the file in case it was saved somewhere other than your documents folder.

Yep.^ Implied question: How did you check for the file and were unable to find it?