[When the story begins, the late Halliday has just willed a major prize to whosoever finds a unique, hidden easter egg in his VR realm, the OASIS. The terms of the will would give the finder his multi-billion-dollar fortune, along with administrative control over the OASIS itself.]
Just to butt in with an answer, I'm rather certain RoosterTeeth themselves said on one of their podcasts (will look for a link) that they had been approached with the offer to have Ruby or at least her weapon appear in the film.
So the likelihood of that not being fake is higher than other pieces of vandalism.
Edit for clarity's sake: https://youtu.be/Ap9hKudGHk8 at ~20:24. Burnie confirms that they, at the very least, signed the release so that Crescent Rose could be used. So this very well seems real.