Board Thread:General Discussion/@comment-3003995-20141017010235/@comment-10301320-20150422063618

It could very well have been her Zanpakuto, after the wielder dies there's nothing to say the former Zanpakuto doesn't go back to being an empty Asauchi but perhaps with it's former sealed appearance from when it was a proper Zanpakuto. Heck, she could have even had a basic Asauchi the entire time she was with the Gotei 13. Is the simplest and most obvious reason as to why he took the sword out of her coffin at all, so that's probably the most likely answer.