Only seen a 747 nose gear pin installed once in my life, then only after the aircraft came out the hangar.
I can fully understand how the F/E missed this.
A properly installed nose gear pin is visable at first glance by the red flag, remove before flight hanging down from it.
Even if this banner is missing and being so far up you have to look close.
But you still have to check.
For a piece of coat hangar to be put through in place of a pin would be easily overlooked.
Especially if it was a white coat hangar.
Had the F/E found this and reported, what would have happened to the ground engineer, probably nothing.
Kind of like putting clear tape over the static ports for washing and painting.
Hard to detect at night.
But it has happened.
Like most things that happen, always blame the crew.
As crew if we find things like this that we can see, can you imagine what is hidden that we dont see!