outlook problem

In Outlook 2003 I created a sub-folder under a main folder. The main folder is a .pst data file. I accidentally deleted the sub-folder but when I tried to restore it from my deleted items folder in the main folder, there wasn’t anything there. I have searched the Outlook help files but nothing; I also did a search on Google for a solution but to no avail. Does anyone have an idea on how to restore a deleted sub-folder when it doesn’t appear in the deleted items folder of the parent folder?