Where is the key to the second floor of Jingzhe Cave in Qin Gui prequel (Resurrection)?

To get the key to the second floor, you need to get the statue of God of War in Wei Lan's father Blue Bear's room in the main plot, and then click on the huge statue in the sacrifice hall next to Blue Bear's house to get the key. At first, I thought I got it from a box in a sting hole, and I have been looking for it several times.