Interesting piece. I kind of feel like they'll still welcome new ideas from you. (I don't think you botched it forever with them.) Another note here is that it's quite common for publications to cover the exact same topic over and over. (Even this publication, The Writing Cooperative, surely covers the same sorts of issues all the time.) What matters (in my opinion) is the writer's perspective. Remember Alexander Pope's famous lines: "True Wit is Nature to advantage dress'd. What oft was thought, but ne'er so well express'd." The "what oft was thought" part means it's been done before; the "but ne'er so well express'd" part means that your fresh, unique perspective can make it still quite riveting. :-)