'The Journal of the Young Master Xiong'? A journal of one of their family's ancestors?
And why it was said as missing?
They have many journals of their ancestors passed down to them. All of them were safely displayed in the treasure room of the Xiong Mansion.
That era of Huaxia was when literacy was at its peak. The golden age allowed everyone to have a certain extent of literacy. Thus, almost all of the Xiong and Zhou family members were literate. They took pride in it, and loved to write journals to practice their writing. It went on until it became a habit of the two families in ancient times to keep journals and save them as records for the future generations.
Therefore, there were a lot of journals in the two families' collection rooms.
If there was something special about this journal that might affect the treaty between the two families, his ancestors should have found it already.