Well, trying to be more specific this time, what exactly is the lore involving the missing box? I mean with the way you seemingly hyped it up I’m wondering if it comes into play at some point or is found by someone and all?
Don't worry, the Forgotten Box will not remain forgotten in this story. :)
The lore of the Forgotten Box is that it's the Miracle Box that at one point belonged to the Mage who created the Miraculous, Qua Mei. It once hosted twelve kwamis, but after Qua Mei chose to give up his immortality he divided most of these kwamis into other Miracle Boxes across the world with the exceptions of the kwamis of Life, Death, and Magic.
After a horrific Wish made by the merging of Life and Death, and the sheer control the power that Magic could wield, Qua Mei and these kwamis decided it would best if they were not to remain on earth in the hands of humans. Vitaa, Shii, and Uunice had no interest in losing their physical form at this point, so instead they decided to let Qua Mei hide them away. Qua Mei also considered having Fluff in this box as well, but a familiar future Rabbit holder showed him that this Miraculous would be needed on earth.
