it has always been an issue on flights to and from HKG... I can only assume there are organised groups or individuals working these routes and stealing esp on CX flights...CX has listed warnings on their websites...
I am uber careful and carry my wallet at all times in my handbag even to toilet
not sure if pick pocketing was the problem ; sounds like a sleeping passenger was an easy target...and who would know which passenger belonged to which overhead bag...rummaging away any time during the flight...sorry to hear it ...