I have seen one car (in 20-someodd years) that sheared the woodruff key for the sprocket that drives the oil pump and distributor due to a locked distributor. I guess the same would be true of a locked oil pump, but pull the distributor out to check if the distributor is free. While it's out, check to see if the drive piece turns.
Of course the distributor could be 180 degrees out and just moved ever so slightly upward....that would make it disengage from the drive tangs. Check the easy stuff first.