Is this only a single leaf or does the plant behave like this with all
leaves? If it's only a single leaf it's most likely just a growth
disturbance. However if it produces such leaves regulary or always it's
likely to be a mutation. I've heared that a double-pitchered N.
rafflesiana was once found in Kinabalu Park with all the leaves double
pitchered, however I do not know if this isn't just a fairy tale.
Andreas