I really sympathise with you...exactly the same thing happened to me about a year ago. It also had my Garmin, mobile, running kit etc and I was absolutely gutted for ages. Scoured the area the next morning but didn't find anything. Later found out it had happened to other people at my running club in the same pub. Had to keep thinking that at the end of the day, its only possessions (no matter how valuable) that can be replaced. Tough lesson to learn but I am paranoid about leaving my bag closed and keeping it on me now.