I doubt that it was a question of "properly secured". I suspect a LOT of barges got "broken loose" by the winds and storm surge, even though they WERE "properly secured".
I saw one video clip where the Corps of Engineers was trying to "break loose" a barge with a massive crane, so they could use it in fixing the levee breaks. The barge had been broken loose and washed well up on shore, and they were using the on-board crane and THREE tugs to try to pull the barge back into "floatable depth water".
You and I may see that, but I doubt a lawyer would agree with that.