These days many hotel mini bar have a weight sensor which detects weight change, and the system will automatically charge to the room if weight change is detected as mini bar items consumed. I do not remember if Conrad Hong Kong had such system when I stayed there two years ago.

Hotels with such mini bar warn guests in writing not to put any of your personal items in a mini bar fridge, since that can trigger the sensor and have items billed to your room. Some hotels will have in writing if placing your items in mini bar fridge triggered mini bar charges to your room, then you are responsible for payment regardless of if you consumed items in mini bar or not.

I think best you can do is to correspond with Conrad Hong Kong directly via e-mail or phone, not corporate customer service, and see if the hotel will reverse the charge or not.