[ShadowHeart]

I dunno about any text on it.. however.. after the canon is moved, you see a cut scence in Shinra HQs with Scarlet and Rufus. Scarlet says something along the lines of "this new weapon will be called the Sister Ray", implying that it wasn't called that before.

In either case, 2 WEAPONs are killed by that canon. And if you say "the weapon that was killed by the Sister Ray" and don't specify any further, I'm automatically going assume that you mean Diamond WEAPON, as it was killed by the Sister Ray *after* the scene where Scarlet names it.