Big_Jim
Welcome to the Forum
It is a known issue, but I think you are the first to loose ALL the bolts at once! I have had a bolt come loose in the past but not for several thousand miles! There was a discussion about this, on the list, a while back. I am almost sure that the advice in the Rohloff manual used to say to loctite them however in the current manual there is no mention of loctite.
As for the oil leek I have heard a story of someone on tour who carried on going for over a 100miles with effectively NO free oil in the hub (Not recommended). At the next city new oil was added and he continued on his way. The thing is that even if all the free oil drains out there is still oil adhering to the gears. IF the story is true (it may be internet myth) then I very much doubt that 4km will have done any damage.