Absolutely right! I don't know why everyone is being so sarcastic towards OP - I find the alleged incident entirely credible. If you set off the detector (which can occur as a random event) you may spend a minute or so being frisked by a security guy which is easily time enough for anyone (security or another passenger) to help themselves to any valuables that have passed through the machine and are lying in a tray. I always put wallet and watch in my carry-on and zip it closed, and would urge others to do the same.