Oh Wait, This Is My Grocery List

Basically, somebody writes down a safe combination, a speech or poem, plans for the Death Star, etc. onto a piece of paper. So they reach into their pocket, pull out a list, and more or less go.... "Now that's done, let's see what else I must do. Butter, eggs, litre of milk... wait, no. That's my grocery list", puts it away, pulls out another list: "Okay, let's start again." A variation has a messenger handing at first a grocery list instead of the intended message to its recipient. Another variant involves someone taking out the wrong sheet of paper with a list of laundry items. Not to be confused with Bread, Eggs, Milk, Squick, except in the most literal examples. A subtrope of Unfortunate Item Swap. See also Script Swap. This may be one response to an Shockingly Expensive Bill.