Every year tens of thousands of people write down little “idea anecdotes” for books, then they put aside and never actually do it.
Then some professional writer happens to produce a similar story, because his/her stream of inspiration is similar to yours, and boom: “-this writer stole my story idea!”
This happens every year, a ton of cases go to court just so they find out that “ideas” cannot be copyrighted.
This is why many “professionals” make fun of the “idea guy”.