If someone starts the theft with a thrown rock to your noggin ... you are in trouble.
It was a common tactic of flash mobs that the "signal" which triggers the coordinated attack is that one of the mob members is designated to hit the victim in the face with a thrown baseball or other object. Twelve inch softballs are not really that soft BTW...
If you just get jumped the assialants are going to get your phone / electronic device, and go for your wallet. If you are carrying concealed, they may come across your firearm, they may miss it. But if you're carrying it openly they definately won't miss it, and I think that if you are attacked while OC'ing - it's more likely to be explosively violent, brutal and decisive - as in a bludgeon to the head, because the assailants already know you're carrying, they've decided to attack you despite that, they know they have to at least knock you out if not kill you to keep you from deploying your weapon.