In the spirit of "other people learning from mistakes" - our R44 was oversped a good few years ago and the cause was not the common open throttle but the pilot lifting to hover whilst not being completely aware of his surroundings, which introduced excessive yaw, then in an attempt to get to a "place of safety" away from other things pulled in excessive collective too quickly which meant the governor couldnt keep up.
The pilot then continued on his flight and susequently another pilot used the aircraft - it was maintenance staff that heard the event that later grounded the aircraft.
It cost us £30K+ but was insured, took months to sort out - lots of time and effort.
In My Humble Opinion - Lessons to be learned;
1) State of mind - don't fly if you are mentally distracted/tired/drunk/out of currency etc.
2) Discuss and have a plan - if the reaction to yaw would have been lowering the lever - different story
3) ALWAYS STOP and take stock immediately/ASAP after any unexepcted event - you may be in some level of shock or done something you havent considered - seek wise counsel. NEVER IGNORE IT AND/OR ASSUME IT WILL BE OK.
4)REPORT IT
CC