I read that Sai Baba attended Dev's Udyapan ceremony. How did he attend, and why was Dev initially so disappointed?

Sai Baba did indeed attend Dev's Udyapan ceremony, but he did so in the guise of a Sanyasi. As mentioned in chapter 40, Baba promised Dev he would come, and he fulfilled this promise by arriving with two other companions, all appearing as uninvited guests. However, Dev failed to recognize him, thinking the Sanyasi was just some guest who came for a meal. Because of this, Dev felt disappointed and even believed Baba had deceived him. He expressed these feelings in a letter to Jog, complaining that despite Baba's promise, he experienced nothing special. It was only later, when Jog relayed Baba's explanation, that Dev understood the truth of what had happened.