There are a lot of factors that can cause the files to get deleted and it is difficult for us to determine the cause if we don't have the same device or a pattern of the issue.

If you have already exported the project as .kine file, you can import it back to KineMaster. If that's not the case, it is out of our hands to help you recover the project files. However, to check the issue in details, if there is any pattern that you notice before the projects get deleted, please tap on Email Support below and let us know the exact step taken before the projects got deleted.