Contractor, my point exactly. Some tug drivers have been known to be impatient and "help out" . The pin in question was a rogue and traced to it's owner.
As BOAC put it so veeeerrrry very neatly. "A wise man checks the holes", not the pins. I was fortunate and became a little bit wiser due to my colleagues misfortune. I freely confess I would most likely have missed a non flagged pin on this particular type. The nose gear doors are virtually flush with the hole and require a specific look, so easy to miss, in the dark, on earlies, again, in the cold and wet, and you've already seen 3 pins in the flight deck check before you left the warm and dry.
I merely pass it on so other others might not get caught.