This does not work in OS X 10.10.4.
With System files set to "are included" and File visibility set to "Visible or Invisible" it still can not find the file if I am in the Library folder or above.
I have a file in ~/Library/Developer test.txt, but even with these two options you mentioned it wouldn't work
Searching in it ~ doesn't bring any results
Searching it in ~/Library doesn't bring any results
Searching it in Developer does work
My Library folder isn't even hidden anymore.
Xcode has snippets, most of the snippets are in the Developer folder, but not all.
I wanted to search for .codesnippets on my disk, but it didn't even find the ones I know of.
So I tried it with a testfile. I am very suprised, that spotlight did not let me search my files.
Terminal did its job good:
sudo find / -iname "*.codesnippet"