I have had this mousehole locked down in my house since 2 years, and now it is gone. I have a screenshot of my house made by the end of October, where the mousehole was still there. Shortly afterwards, I entered the customization mode of the house (for the first time after the house was built), afterwards it was gone. I didn't change anything in the vicinity of the mouse hole. The moving crate is empty. I assume there is a bug with house cutomization that deletes certain items under certain circumstances. As I am using the Enhanced Client, it may also be connected to the client. So, be careful people when you customize your house! Some items could be deleted.