Sometimes you can get something to show up if you type the name of it in the Search box in the Content Library.  You might look at the Runtime folder in your original download to see what the directory structure is for it.  You can look under the Libraries directory in  your original content to see the name of the original .pz2 file so that you know what to search for.  If worse comes to worse you can use the "Import" function under "Files" in DS4.