The Hornady powder cop die is not the same as the RCBS lockout die.
The Hornady powder cop die only indicates the level of powder in each casing.
Once adjusted you will see a white line showing that the powder level in the case is good.
This means that you must pay attention to the die with every pull of the handle.
If you were paying attention in the first place you wouldn't have run out of powder.
The RCBS lockout die on the other hand will stop the press from cycling if there is no charge or a double charge.