Black Friday Sale failure - call to action

I did.

I bought NX with the intention of getting a pet and its equips.
I was able to get the pet, since they did go on sale. But the equips didn't, so I don't have any.
Right now I am faced with the option of either buying more NX to buy the equips at full price (which makes the NX I already bought essentially useless), or not doing so and having the NX I paid for the pet go to waste (since a pet without equips is useless).

That's not their fault that you went and bought NX beforehand. Perhaps you should read their policies. They reserve the right to change the game without owing you anything. Even if they didn't, they still don't owe you.