Even without looting; when stores are still open and selling; essential items like gas cans, water cans, fishing gear, generators, food, animal feed, and anything else you can think of will disappear immediately. I was a witness to this effect during the recent midwest ice storms.
Do not even think of depending on what is on-hand in the stores during any kind of emergency.

Have it on hand, have it ready and maintained, be prepared.

Jon Davis