Put the folllowing in "oops-guix.scm":

(use-modules (gnu packages))
(specifications->packages '("hello"))

then do: "guix shell -f oops-guix.scm" to make an environment
with "hello".  I get:

> guix shell: warning: no packages specified; creating an empty environment
$ which hello
> /home/regulator/.guix-profile/bin/hello # <-- not from the new environment!

Or even simpler: do "guix shell -f non-existing-file.scm":
> guix shell: warning: no packages specified; creating an empty environment

Looks like "-f" is ignored entirely?

Version information:
$ guix --version
guix (GNU Guix) 0

(Didn't there use to be a commit?  Is confirmed on #guix as
reproducible ...)

Greetings,
Maxime.