I have SuSe 13-1 on my IBM X60s laptop with KDE. I have started to download a program or two and in the middle change my mind. I was browsing my computer to see if there was a way to clean up the hard drive of unused fragments and so on. I found a cleaner for cookies and so on - but none that address file fragments.
There won’t be file fragments. There might be files.
If you downloaded but did not install, then there might not be much to do. It depends on the program that did the downloading. Often files are first downloaded to a temp directory, then copied/moved to final location. And routine temp directory cleanup would probably eventually deal with it.