Iv done this a few times now. Just ordered a locker to replace it with this time. Although it can happen on the road its usually caused from damage off roading. If you "wind" the diff possibly when a wheel is airborne or in soft mud then suddenly get traction there is a huge amount of force put through the planet gears usually resulting In the gear failing which in turn causes the pin to shear when lumps of metal get stuck between the gears.
Hope your new diff lasts you longer than mine have. Do you do much off roading? If so it may be worth investing in a 4 pin diff. Much stronger than the 2 pin ones.
Cheers mark