It may have been auto-archived:
1. Open Outlook.
2. Click
Tools.
3.
Options.
4. Click on
Other.
5.
AutoArchive.
This is where you will have to check how often you have this set-up. To locate the files you will need to click on Browse > then search for where these folder are placed.
Hope this helps.
happily using
The Message Center Exchange Hosting