I've holes chewed in multiple pitchers here in the North Carolina piedmont
and my Mom has reported the same thing happening to her S. flava in the NC
mountains. I don't think it is slugs doing it to my plants. For one thing,
I don't see any slug slime trails left behind. Secondly, I've seen the tops
of several pitchers chewed off. I don't think a slug would travel all the
way to the top of the pitcher for a meal and I also doubt these wimpy
pitchers (on my S. minor) could support the weight of anything very big.
The damage I see is more consistent with Japanese beetles. I haven't been
able to catch the perpetrator even though I've checked both during the day
and at night. In your case it could be an insect that the plant trapped
eating its way out. Let me know if you find out!
Phil