More to explore:
MYSTERY KEY STORIES ( with lifted lines): I am definitely doing this this year! Something to do with all of my old keys.
Mystery Keys - a creative writing activity for advanced elementary or middle school students
MYSTERY KEY STORIES. Really cool idea for a creative writing idea OR just a 10-15 minute activity. This site has lots of other interesting stuff as well.
MYSTERY KEY STORIES ( with lifted lines) - creative writing prompt