You might have missed something last time! Something delicious like old condiments or that frozen dinner that you're not sure if it's still good even though it's frozen!
The college student scramble. In Poland the most common name for male genitals is "eggs". So opening the fridge, scratching Your balls and then closing the fridge is called a College Scramble.
I'm not sure how you'd pull it off, but it'd be fun to prank someone by making a treat appear in their fridge between checks, even though they live alone.