How frustrating!!! I've been there! What I learned to do that sometimes helps; when the person answers that usually transfers you to voice mail, tell them that you have left several messages and no one is returning your calls, then ask them to either give you to a supervisor or transfer you to an actual person.
If that doesn't work, could you drive back to the office or is it too far? Were they supposed to send results to one of your other docs? If so, ask them for the results. Also, I've done this several times, go and sign a request to get your copies of the reports. They will usaully print them right then.
Good luck, let us know what you find out!