Oh-oh. Here's something you might want to get into the habit of doing when you create skins. After every modification, make a new .wba file; that way, if you ever lose what you're doing or mess up when adding new things, you have your old .wba to reapply and get your old stuff back.
Here's the steps I would go through to modify an existing skin.
1. Open skin studio.
2. Choose "open skin" and find the skin you want to modify.
3. Choose "copy"
4. Give your copy a name and wait for SkinStudio to create the newly named skin.
5. Choose the newly named skin from the list and click "edit skin".
6. Now, before you make changes to the skin, go to the files, skin properties, and change the name, put in your name as the creator, etc.
7. Make the alterations to the skin, save changes, and create a .wba file, then close the skin.
8. When you open Windowblinds, go to "skin options" and choose "rebuild list" and your newly named skin should be there.