In a story I'm working on, the heroine takes off a ring to wash her hands and leaves it on a sink.
The first time one of my critique partners heard this she said, "that ring better show up again."
Well, it does. A whole plot point hinges on it, in fact. But a recent news story made clear to me that there were more realistic ways to deal with the dilemma. Still, I like that ring. Tells us something about the characters and how they interact with each other, even if it's no longer entirely necessary to set them in motion.
After hearing the pesky news story, I had to go back to a scene in the beginning of my story and add another little bit of business to explain why "they can't just do that." Because this is a romance, damn it, and a forgotten ring is more fun and juicy than a paper trail.
Maybe they'll both work out. Maybe they won't. It's still a work in progress.
So where'd this notion come from, anyway, that you can plant evidence but not props?
Anton Chekhov, apparently. In an 1889 letter he wrote, "One must not put a loaded rifle on the stage if no one is thinking of firing it."
He became so enamored of the line, he used it at least twice more: "If in the first act you have hung a pistol on the wall, then in the following one it should be fired. Otherwise don't put it there"  and, "If you say in the first chapter that there is a rifle hanging on the wall, in the second or third chapter it absolutely must go off. If it's not going to be fired, it shouldn't be hanging there." 
I used to agree. But you know what? I'm not so sure anymore. Chekhov was a Russian. He should know all about misdirection and red herrings, right?
So I'm keeping my blasted ring for now. Until I figure something else out.