Staff styles are still available within Finale. Styles which were previously included in older templates have been removed because of changes in Finale. I believe the single line staff style is still included in Finale, so you should be able to apply that style to your score. It is not part of the problem with the library file. The problem with the library had to do with how the whole package was compressed for digital delivery.
Remember, as long as you are using a template file, there is no need to use the library file. If you do need the library file for working with a non-template document, it is possible to open a blank template file, then save the percussion library elements separately. This would allow you to create your own library file.