If you were denied a modification, I wouldn’t consider a short sale a slamdunk. I am in a similar dilemma (underwater, want out) and my short sale was rejected because I wasn’t distressed enough. Your sob story has to be a real tearjerker. Don’t bother pointing out that your loan is non-recourse. My experience is they don’t care.
Incidentally, I haven’t made a payment since March and I called the County recorder this week–they haven’t filed a NOD yet. My theory is they’re praying that prices continue rising rather than take the hit. There’s your shadow inventory.