I now have the official, required Library of Congress copyright investigation complete so that the Long-Forgotten Movie can be digitally duplicated.
Except, well (using Facebook relationship status-ese) -- it's complicated.
The investigator discovered that, yes, the Famous Rocket Company applied for a copyright, but that was for an *unpublished* work - - almost a year after they donated the film to the Not Very Famous Museum. The museum had already shown the film to close to THREE MILLION cash-paying visitors, so it was hardly "unpublished" anymore. By the timeline, the Famous Rocket Company was trying to copyright a work it had already given away. Based on this history, the Library of Congress researcher declared the film's copyright "questionable."
The Famous Rocket Company listed the Famous Director as "author" but since it's a work-for-hire, that probably takes care of the Famous Director part of the copyright claim equation.
It's going to be a long summer. Hope for the best.