Rudder failure

Last weekend Jan 2nd our skiff was out under lively conditions. At the end of the session after a bit of rowing upwind and into the relatively small seas (waves about .5m) the cox turned the boat and started going downwind. After a turn to return to the the clubhouse while approaching the beach the cox was not able to steer the boat. Our observers on shoreside saw that the lower part of the rudder was missing and advised the cox on the condition. The cox stopped the approach and backed the boat and headed out, steering by commands to the rowers. He then made the approach using oar steering and made a safe return. Upon inspection we found that the rudder had broken at the transition from the rudder head to the rudder blade. Inspection of the fracture area suggests that the blade flexed sideways and broke under a bending stress at the transition line. 

Has anybody had a similar experience or know of rudder failure cases?