CWG - a little misleading ... IMHO
If after issuing a subpoena, the party then capitulates, then yes, you are correct, we may not know about this.
If after issuing a subpoena, the party continues to OBJECT, then the objection IS filed in court, because it means the x-day rule (I forget - 3 or 5 days) is invoked, per the examiner work order, THJMW then would rule on the subpoena.
So, accurately, a challenged/refused subpoena, we would hear about via a court filing, and an ultimate ruling.