If all the leaves were like that... it could be an interesting trait. What could possibly go wrong with more leafage right?? Well.. besides shading out leaves beneath it.
I would clone that branch, and see if you get more of that action... and clone that specific leaf and hope it grows. Isolated to the specific affected area might be a step in the direction of a plant that is all like that????
Or maybe its just a random thing that might not happen again.
I had this exact same effect on a hermaphrodite, It began as a female that was re-potted. After going hermie from stress i harvested, re vegged and during the re veg process a leaf produced the same mutation.