To diagnost the issue with disappearing photos and files from your phone, try the following steps:

1. Check the settings for photo and file storage for your phone.
2. Verify that you are still connected to the internet.
3. Confirm that your phone has enough free space still to accomodate new photos and downloads.
4. Check for any updates that might have changed the file saving location.
5. Try resetting or rebooting your phone.