We don't index every recipe on Food52 in our blog index. Food52 requested that we only index tested recipes that they can stand behind - those would be Featured Recipes, Genius Recipes, and Community Picks which currently number 8,662 recipes. All other member submitted recipes on Food52 that are untested are not indexed by EYB.
If you want to add a Food52 recipe to your EYB Bookshelf, you will need to add it as a Personal Recipe - explained here in Help. You can enter the link in the Online URL field so it then appears as an online recipe in your searches, though not as part of the Food52 blog.