Why is no mention made of the reaction, of Balak’s officers who were accompanying Bilaam, to the talking donkey or the revelation of the angel?
The Daas Z’keinim and Paneiach Raza write that the angel killed the officers who were traveling with Bilaam, which explains why no further mention is made of them. Rabbeinu Bechaye explains that they were traveling in front of Bilaam and therefore didn’t observe or hear the commotion and exchange between Bilaam, his donkey, and the angel. Alternatively, even if they were present, they weren’t on the same spiritual level as Bilaam, and they were unable to see or hear anything out of the ordinary. Rav Aharon Leib Shteinman suggests that even though they witnessed and heard the exchange, the officers didn’t reflect on the miraculous scene that they had witnessed and it made no impression on them to reconsider the propriety of their plans, so no reaction was mentioned on their part.
From:Parsha Potpourri Points to Ponder
Perhaps they were astounded, but the pasuk does not mention it, because it is not relevant to the narrative.
Where were Balaam's two servants during these discussions and events? Where were Balak's officials and dignitaries? Not in the dream! Only in the morning, when Balaam awakened and actually set out on his way, were they with him. Likewise, as regards the contradictory stance, as it were, of the Almighty (Question 8 above), only if one does not pay close attention to the structure of this description does it seem that G-d, after giving Balaam permission to go, was angry at him again, and then in the end He once again changed His mind and permitted Balaam to set out. But this only seems so if one does not distinguish the general heading (v. 20) from the details of the dream that follow. The inappropriateness of some of the angel's remarks as well, stem from the fact that Balaam was dreaming.
R' Schwab in Maayan Beis Hasho'eva uses this question to answer two other questions (My summary looks long, but it's really pretty brief).
He is bothered how Chazal knew from the words כי הולך הוא (Bamidbar 22:22) that Bilaam was going out of a desire to curse Israel:
כי הולך הוא" - ראה שהדבר רע בעיני המקום ונתאוה לילך"
And his second question is why Hashem got upset with Bilaam for going, put an angel there to stop him, and then told him to go again!
וַיָּבֹא אֱלֹהִים | אֶל בִּלְעָם לַיְלָה וַיֹּאמֶר לוֹ אִם לִקְרֹא לְךָ בָּאוּ הָאֲנָשִׁים קוּם לֵךְ אִתָּם וְאַךְ אֶת הַדָּבָר אֲשֶׁר אֲדַבֵּר אֵלֶיךָ אֹתוֹ תַעֲשֶׂה:
Hashem says go with them
וַיִּחַר אַף אֱלֹהִים כִּי הוֹלֵךְ הוּא וַיִּתְיַצֵּב מַלְאַךְ יְהֹוָה בַּדֶּרֶךְ לְשָׂטָן לוֹ וְהוּא רֹכֵב עַל אֲתֹנוֹ וּשְׁנֵי נְעָרָיו עִמּוֹ
Hashem got upset that he went, and sent an angel to stand in his way
וַיֹּאמֶר מַלְאַךְ יְהֹוָה אֶל בִּלְעָם לֵךְ עִם הָאֲנָשִׁים
The angel said to Bilaam "go with the men"
Rabbi Schwab then points out that the escorts were with Bilaam both before and after the encounter with the angel, but seem to be absent at the encounter:
וַיָּקָם בִּלְעָם בַּבֹּקֶר וַיַּחֲבשׁ אֶת אֲתֹנוֹ וַיֵּלֶךְ עִם שָׂרֵי מוֹאָב
Bilaam went with the Moabite ministers
וַיֵּלֶךְ בִּלְעָם עִם שָׂרֵי בָלָק
Bilaam went with Balak's ministers
Rabbi Schwas explains as follows: Bilaam was only permitted to go in the first place for his own honor, and was not permitted to go with the desire to curse the Jews - Rashi to 22:20
אם לקרא לך: אם הקריאה שלך וסבור אתה ליטול עליה שכר, קום לך אתם
"If they have come to summon you" - if the summons is for you, and you assume to be rewarded for it, then go with them
But Bilaam ignored this caveat of the instructions to go, and instead went with excitement to curse Israel. He was so excited and personally invested in the mission that he actually sped ahead of the honor guard that was with him! Seeing that כי הולך הוא, that he was going alone, that he was excited to go curse the Jews, Hashem sent an angel to stop him. The angels instructions were not to turn around - the instructions were to go with the escort, meaning to go for the honor that they are according you and not for the sake of the mission itself.
So, the ministers were indeed not there, as Bilaam had sped ahead in his excitement. This itself was the reason that his going was problematic.