Unless I missed it, the FBI still hasn't disclosed how they tracked down the physical server. The FBI said was it was "located in a country with an arrangement

Unless I missed it, the FBI still hasn't disclosed how they tracked down the physical server. The FBI said was it was "located in a country with an arrangement with the US, who gave us access", but remained intentionally vague and said nothing more. Can they really use that data without disclosing how they got it?