So you're right in that it was retroactively protected by copyright the moment it was written, but, without more information than this, it seems at least possible that the copyright on this work has now expired.
It says that it should follow 302 as if it was published in 1978 if it was not heretofore copyrighted, and it wasn't, and it should follow section 302 which starts with
"Copyright in a work created on or after January 1, 1978, subsists from its creation and, except as provided by the following subsections, endures for a term consisting of the life of the author and 70 years after the author’s death."
