Find labels of positions not executed through cbots

Let's say I want to find and modify or close a position which was created through the default buy or sell buttons of ctrader and not via bot, how do I find this position? I understand positions created this way do not have a label. 

This is the code I tried to no avail:

if ((Positions.Find(null, Symbol, TradeType.Buy) == null))

Also tried this, basically leaving the label blank but putting quotation marks:

if ((Positions.Find("", Symbol, TradeType.Buy) == null)