I personally know people who went down to help rebuild New Orleans and had their entire truck and trailer, which were full of tools, stolen while they were down there, so no it is not an urban legend.
And I don’t see why residents can’t start filling sandbags when storms are forming in the gulf to reinforce levees like a flood.
I''m sorry, when I initially read your post, I thought that you were referring to a story that was making the rounds at the time about rescue helicopters being shot at, a story that turned out to be untrue.
I am truly distressed and mortified that your friends who traveled down here, purely out of the goodness of their hearts to help in the rebuilding process, lost their valuable property. I do want to say, without equivocation, that the people of New Orleans are grateful and humbled beyond expression at the outpouring of goodwill that has come our way since Katrina. Please do not let what you see on the news and the negative stories that you hear about the recovery efforts completely color your idea of the city and it's people. Very often things are not quite as cut and dried as they might appear. The bad stories about an event are frequently magnified by the media, while the the more plentiful mundane stories of regular people picking up the pieces of their lives and moving on after a life altering event, are often overlooked and considered boring. I hope your friends know that their contribution in our time of need was/is greatly appreciated and that we say prayers of thanks for every one of them.