I am very sorry...
to read about your story Kari.
Enough have been said already and I can't provide any new insights to what has already been provided by the various members.
From my own experience, if i travel with an extra watch in my laptop bag or a carry-on bag, the one thing I always do is to do intermediate checks in between my various encounters.
So before and after security check, I always check the bag by feeling/ looking in the bag that the pouch is still there. At almost every stop on my way to gate or before leaving a store/ lounge etc, I do this...so i have a satisfactory feeling it is still there. In the event the worse may happen, I don't need to retrace all the way back but only up to that particular point.
During my flights I take out my bag at random times and do the same check - not extremely frequent and also not that obvious of course. Prior leaving the aircraft, I again check.
I know this is not helpful, but in the explanation/ clarification it doesn't seem intermediate checks were done... it possibly may have been detected earlier in that case.
I hope it will turn up soon and that it will wash away the disappointment.