Musar על גיטין 69:16

The next difficulty is: How could a righteous son loved by his father not inform his father that he was alive and save him an untold amount of anguish? Even if Joseph had found himself at the end of the world, instead of in a country bordering on the land of Canaan, was he not duty bound to let his father know that he was alive instead of letting him suffer pain for twenty-two years?