Super Sapper Charge

Hoping someone knows what to do because I've spend the last 2-3 days trying to figure this out.
I recently re-rolled engineering on the TBC Anniversary servers and have gotten it to 375. After crafting a bunch of items I wanted to get some Super Sapper Charges to test out the aoe damage. This is where I got stuck. I can't figure out how to learn the recipe.

I have not been able to learn it from any of the engineering trainers. I'm pretty sure it's supposed to be learned at skill level 340 from what I could google on the subject. Wowhead doesn't show where to learn it either. I also have my goblin engineering quest done and the membership card so I'm geniunely stumped.
Has anyone else run into this issue or is there a perfectly normal explanation for it that I've missed?
Thanks for any help you all can offer!