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This sounds awful but in reality it is no big deal. The truth is that although writers are often derailed about having their ideas scratched, this happens so rarely that you have more chance of being savaged by a runaway yammer than of having a story line ripped off. It is not worth losing any sleep over. You will get sick.
There is no copyright on ideas, only on the exact way the words actually appear on the page. So unless someone lifts whole sections out of your article or story, word for word, there is no real way to prove you have been robbed. You can sprinkle copyright notices all over your work but it offers about as much protection as crossing your fingers and reciting a magic spell.
Be philosophical. Ask yourself: is it worth trying to sue someone for breaching your copyright if he/she lives on the other side of the world and getting him/her into court would bankrupt you?