Your question is not quite clear to me, but I think what you mean is that the folder exists on your Hard Disk, but you can't see it in your OE. Right?
Since you can see it in your Hard Disk, I once again assume that you are aware of folder location, etc and the folder is in right place but is not visible in OE6.
On these assumptions, I offer this work around.
- Remove that OE folder's .dbx file from its current location and keep it somewhere else.
- Now open OE and create another folder with exactly the same name.
- On completion of previous step, a new .dbx file must have been created in the mail folder location.
- Now replace this new folder with the old folder, hopefully all your mails stored in that folder will be back.
Hope I have understood your problem correctly.