Board Thread:General Discussion/@comment-6192846-20130913170916/@comment-6192846-20140524145445

This got referenced as early as Epic of Evil:

(from Gumillia's aftermath section)

"But, after the Duel of Merigod Plateau, she disappeared from center stage."

しかし、『メリゴド高地の決闘』の後、彼女は表舞台から姿を消すことになる.

(from the caption next to her picture)

"After the Duel of Merigod Plateau, where might she have disappeared to......?"

メリゴド高地での決闘後、彼女はどこへ消えたのだろうか・・・・・・？

The assumption was The Last Revolver took place around the same period but this reinforces the idea she was actually there.