I thought perhaps if it was a newly planted banana plant, perhaps it was too deep and the pup had plenty of space to reach out so far.
I have had similar occurrences when a bermuda border was in the way, or an old root from a since removed oak tree being in the way. Perhaps a big old root or something buried made the pup travel what seems so far?
Anyway, cut it as close to the mother plant as you can, a digging bar makes it very easy.
Check out this photo from the diagrams gallery:
Banana Gallery - Banana Diagrams
