The article seems to presuppose absolute anarchy. In reality governments that have collapsed in the past seem to do so because of large factions fighting it out; i.e. Sulla and Marius in the last days of the Roman Republic. This does not mean one should not have food stored to help when stores are closed; it does mean one will probably join a large faction and fight. Portable foods, rather than a fixed location, will be the most desireable.
It's happened before, AP.
2005 - Katrina;
1992 - Los Angeles;
1977 - New York City
Maybe only a few days (in katrina's case, weeks), but the conditions of anarchy have happened before. Civilization is only a veneer over the savages.