Why does Uninstall say "Nothing was found to remove"?
Short answer: The app has usually already been removed (for example dragged to the Trash or by its own uninstaller). Refresh the Apps list.
The app and its files weren't where Storage Studio expected — usually because it has already been removed, for example dragged to the Trash or deleted by its own uninstaller. Refresh the Apps list and it should disappear.
If you still see leftovers you want gone, check the Trash first; Storage Studio never guesses at files that don't clearly belong to the app.