I do well over 100 sectors per year and have been doing so for a number of years and I have never, ever had an item stolen from my luggage while in the care of an airline. I have had bags lost completely on occasion though. Also, I often stow my laptop in my hold baggage if I don't need it or don't want to carry hand luggage.
In my experience it's the thieving b*astards who work in hotels you need to worry about, I've had all sorts of things stolen from hotel rooms, even my wedding ring on one occasion, try explaining that to the wife, though she knows I never wear it when sleeping so she accepted my explanation of forgetting to put it on the following morning and it not being there at the end of the day. I've also had things stolen from those in-room safes.