Missing orcalculum+ for Ultima Weapon

I’m literally missing a orcalculum+! I just started gathering them, and gathered the one from Pirates in the chest and the one from final world in the chest. It said I obtained one both times but my invetory only says I have only one! Went back to the chests and they are both opened.

Like what? Am I not going to be able to get the Ultima weapon now?

If you opened both chests, but only have one in your inventory, then it sounds like you visited the Moogle Workshop prior to obtaining the other Orichalcum+.

Each time you visit the Moogle Workshop, all currently possessed materials (including Orichalcum+) will be moved out of your inventory and into the Moogle Workshop.

To verify this, open the Moogle Workshop menu and view "Materials List". This will provide a list of how many materials you possess for synthesization.