The original pattern for this goes back to "Kidstuff", a nifty little 'zine for teachers/librarians that was around in the late 80s and early 90s. Each issue had a story theme, complete with books, reproducible patterns and other neat stuff. We got it at the library and I still have 5 out of 6 volumes worth in notebooks in my office. I still occasionally find useful tidbits in it.
You could play a "who's missing" game with any kind of animal, but the "whooos" makes owls perfect for this and the kids love it. You could easily make the owls from flannel or paper and could add on more if wanted, though I think 6 is plenty for the preschool set. My two year olds tend to be more challenged by this, but there's always one extra observant one in the bunch, and my older kids would gladly play this for the full story time!