Why can not get the special item after purchase ?

[jmpc]

After purchased 1 set of this month item Demonic Gazzer. I should get Khinos Dragon Blade.
But no this reward found in my inventory.

[Ryosaeba]

This happened last time with the mages. It specifically said 1 set to get the prize. But my guild mates confirmed you need 4. The "1 set" should definitely say "4 sets." Very sketchy advertising.