It sounds like if both the input and output device is gone from the sound panel on OS X it must be a hardware failure. OS X can not communicate with the device even if it finds it. The chips are on the logic board so it sounds like you need a logi board repair. Do you see a light inside the headphone jack? Not sure it would help since the digital output can hang sometimes and needs to be reset. But if OS X does not list in and output devices it can not communicate with them and it seems to be a hardware failure.