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

Dev felt deceived because he had earnestly invited Sai Baba to his Udyapan ceremony, and Baba had promised to attend. However, Dev was expecting Baba to appear in a recognizable form or for a clear miracle to occur. As Chapter 40 describes, an unknown Sanyasi arrived with two companions, and they were fed. Dev did not recognize this Sanyasi as being Baba in disguise. Because he failed to witness what he considered a clear fulfillment of the promise, he believed Baba had not come. This led him to feel disappointed and write a letter to Jog complaining that Baba's words had turned out to be false and that he didn't understand why he was let down.