If you deleted your files by accident, you can recover the files from File Cache.
Please note that only iOS 11.0 or later version supports File Cache. File Cache can save the content you edit within a week.
Please follow these steps to recover the file.
1. Launch XMind for iOS,
2. Enter Settings > File Cache,
3. Find the file you need,
4. Slide left and select Retrieve,
Then the file will be recovered and show in On My iPhone.