In שמות ב:ו it says, "והנה נער בכה" - "and behold a lad was crying". The basic interpretation is that this refers to the crying baby Moshe who sounded older than he was (Rashi) However the Medrash יל''ש ח''א רמז קסו says this lad is referring to Aharon, who was nearby overlooking alongside their sister Miriam. The Ba'al Haturim agrees and says נער בכה =זה אהרן הכהן (Same numerical value)
My question is according to the Midrash and other Rishonim who understand it this way, why does the Torah in שמות ב:ד state "his sister [Miriam] stationed herself at a distance" but omit "his brother" (Aharon)? Any suggestions?