The Purloined Letter Approach

"The Purloined Letter Approach" is the general name of a plan to hide something in plain view. The technique is also referred to as Hiding in plain view.

Origin
The name of this idea is based on Edgar Allan Poe's detective story "The Purloined Letter", where a damning letter is hidden for ransom. Despite the best efforts of the police, they cannot find it—even knowing which room it is in. Finally, the main protagonist of the story describes how very small changes to the letter caused it to be hidden from the police's eyes, even when they saw it, simply because it didn't look quite the way they thought it should.