Why did Dev feel disappointed and write a letter to Jog after his Udyapan ceremony?

Dev's disappointment stemmed from his inability to recognize Sai Baba, who had attended the Udyapan ceremony disguised as a Sanyasi. According to the account in Chapter 40, Dev had invited Baba with great devotion and was eagerly anticipating his presence. When the Sanyasi arrived with two companions, Dev saw them merely as uninvited guests and did not perceive Baba's divine play. This failure to recognize his Guru led Dev to feel that Baba had broken his promise. He then wrote a sorrowful letter to Jog, expressing his deep disappointment and confusion, feeling that his efforts were in vain and that he had been deceived.