Diesels don't flood, as it's fuel that control's there speed, more fuel more rev's. with petrol air controls the engine speed.
these new auto's can be funny on hill's. the company toyota hi ace van is only new & it has stalled in Sydney on a very steap hill on lights, it will also roll back if i don't hold throtle or keep foot on brake. hard to say what has happened in your case. but main thing is it re started. also have to know what stall speed the Torque converter they have is, but i can't see that causing what happened to you.