Not sure if this will help but Finder Search in Yosemite works slightly differently from that in my Snow Leopard which if not done right ends up displaying a blank.
First off make sure you have highlighted the area you wish to search in the side bar, it normally defaults to your Home folder so for system you need to highlight "Macintosh HD". Enter the file or fold name you wish to search for in the Search Box, this should give you a drop-down showing the same name - select it. Next click "+" to show two more options, for "kind" click and at the bottom chose "system files" and then next to it change "aren't include" to "are included". If you don't have "system files" as an option chose "other" and scroll the attribute list and tick it - select ok and you should then have it available.
If all went well you should see your file/folder name displayed in the window, click on it will the show its path along the bottom so you can navigate to its location.
Have seen various reports that Finder Search can be broken by updates and re-indexing may help but try the above remembering to select search location first in the side bar.