A false hook. Something that draws characters into a module but has nothing to do with real events. A term originating with Alfred Hitchcock. (Warning: because players never believe a GM is lying to them, they will often keep on following a Maguffin).

an object (or less commonly a person or event) that lies at the center of many kinds of story

the "hook" which gets a character inextricably involved in the scenario. This may be a mysterious message or event, a highly-desired object, or any other item that gives a character a stake in the plot. The term was coined by Alfred Hitchcock, who used it to describe the gimmicks he used to grab characters'--and viewers'--interest in his films.