Hi David
Its unbelievable that this has never been noticed by Amateurs. But like you say your wife spotted it. Its probable that we are so used to the bright star pattern of Orion that the arrow as gone unnoticed, I bet there’s lots of these asterisms to be discovered. I will have a look next clear night but might struggle with eta with the light pollution around here. Might take my wife out to a dark sight and see if she can spot anything!
Peter