I dont know where your coolant went....but it didnt pull it from the coolant bottle back to the system,because the banshee system dosent work like that.
The coolant bottle is an over flow only,it does not recirculate the coolant back to the radiator or the system.
90% of banshees I see dont even have a coolant bottle,mine sure dosent.
As far as answering the question that was asked.
Fill it up as much as you can,run the motor for your heat cycles checking and adding coolant in between.
Dan