This is part of the Easter Egg. After completion of the table in the corn field by the power tower, you have to enter the Navigational Card. An error will show saying wrong navigational card unless you do as Richthofen says. The only known spawn for a navigational card is at the Bus S...
Let’s take a moment to recognize all the Studios and teams all (in alphabetical order): Activision Central Design, Activision Localization Dublin, Activision QA, Activision Shanghai Studio, Beenox, Demonware, Digital Legends Entertainment, High Moon Studios, Infinity Ward, Raven Software, Sledgehamme...