Why did Dev feel that Sai Baba had deceived him after his Udyapan ceremony?

Dev felt deceived because he had lovingly invited Baba to the Udyapan feast, and Baba had promised to attend. However, Dev did not see Baba arrive in his familiar form. As detailed in Chapter 40, three uninvited guests, a Sanyasi and two companions, did arrive and were fed, but Dev's mind was clouded by delusion and he did not recognize Baba in this guise. He felt disappointed that he didn't receive the experience he was hoping for. In his confusion, he wrote a letter to Jog complaining that Baba's promise had been broken and that he felt let down, not understanding the profound way in which Baba had actually kept his word.