Connecter will show you a file as missing if you’ve added a custom preview(s) to that file or you’ve linked it with a product and:
You’ve renamed the file.
You’ve deleted the file.
You’ve moved the file to a different folder.
You’ve deleted or moved the folder in which the file was located.
To add a missing file back you’ll need to restore its original name and location.
By default, missing files are hidden. You can show missing files if you go to the Files drop-down menu and check “Missing files” option.