I wonder how much panic and irrationality play into which items people choose. I doubt relatively bland foods (although ideal for survival purposes) like rice, canned beans, and whole grains would be among the first items to fly off the shelf. If I ever had to buy food last minute I've always thought that these items and things like potatoes, brussels sprouts, dried beans, raw nuts, etc. would likely be available because people wouldn't be thinking practical long term, but rather everyday comfort food.