Wal-Mart Fungus Beef Jerky

"I am experiencing a tremendous upset for eating fungus for the first
time in my life"

You've never eaten a mushroom?

Was it Walmart brand? If so, they should work with you on possibly
some sort of discount or free product. If not, then their resolution
of exchanging the product is all they can really do. If you want to
pursue further compensation, I would suggest the company who makes the
product. That's pretty gross, I wouldn't be happy either.

How about they exchange the packet next time you bring it in? That
sounds about fair. I know the difference between jerky and fungus,
even whilst drinking beer. Why should they be punished because they
didn't notice it when you didn't, either - and you were sticking it in
your mouth!
You live in Honolulu and you've never eaten fungi? I take my hat off
to you, as that's not easy to do. Loads of Asian foods have mushrooms
of some variety.