When a Reporter generates a diagnostics file called "reporterdiags.zip", there is a way to find out the serial number of the Reporter beside getting the serial number from the customer or the case details.
There is a file called "telemetry_data.log" under this path "\data\bluecoat\bcreporter\server\system" where it contains the serial number of the Reporter, for example:
..."instance_id":"XXXXXXXXXX"...
So the serial number of the Reporter is "XXXXXXXXXX".