Why was Dev so disappointed and doubtful after his Udyapan ceremony, even though he had invited Sai Baba to attend?

In the account from Chapter 40, Dev felt disappointed and doubtful after his Udyapan ceremony because he failed to recognize Sai Baba, who attended in disguise. Dev had lovingly invited Baba, who promised to come. However, when Baba arrived in the form of a Sanyasi with two other men, a 'veil of Maya' prevented Dev from seeing the truth. He only perceived them as uninvited guests who 'came on his own'. This led to his deep disappointment, believing Baba had not kept His word. His doubt was so strong that he wrote a letter to his friend Jog, complaining that Baba had deceived him and that 'no experience came' despite his efforts.