Thank God.
I was able to track down the problem, using this thread and some .ex fetching with that old program that can grab modules and functions.
The solution, for future reference and anyone else in need, is in finding the .mix folder.
This is completely separate from the elixir/lib folders. Mine was located at C:\Users/Username/.mix . Therein should be an archive folder. Now inside the archives folder was a folder called phx_new, which was actually very old and outdated.
I removed the folder and the error was fixed. This folder did not get removed during uninstall as it was not part of the main env configuration directory tree.
