If you can look into your database, find the module in either the modules or tabmodules table (I'm not able to look into a DotNetNuke installation right now, so I can't check). If it is there, you should be able to manually change the field that determines if it is deleted or not.
These tutorials may have some useful information:
Don't forget to make a backup copy of your database before you do this. You may need to undo things.