Secure erased drive - always one file can be found
When you use Disk Utility to erase the drive, the process ends by actually formatting the drive afresh. In the process, a VolumeConfiguration.plist file is created for Spotlight search indexing.
The file is not a remnant from the past contents of the drive, it is an entirely new file that is created after erasing the drive. I.e. this is nothing to worry about.