It could also be due to a lacking of your news sources because even though Buddhism and Shintoism may be among the respectable religions it doesnt mean they are free of opportunists. Other than the army preventing people going to their homes I dont remember hearing about any looting problems after Katrina, just like you dont hear any now about the Japan earthquake. The news I read in some articles say "little looting" and "no widespread looting" which is different from "no looting"
You also have to consider that if they do take loot where would they put it? Their homes are damaged or if not they are probably already full with whatever they need.