Feng Bufan surely knows Feng Yexuan's identity.
Chu Qianli has even guessed that Hua Rong is probably taken back to Beiming by Feng Qihe.
Though it's unclear what means Feng Qihe used to take the martial arts master Hua Rong.
Anyway, taking him away means taking him away.
Feng Yexuan returned without a word because he knows well that coming back is likely a dead end.
He is prepared to be killed at any moment.
But for the sake of his mother, he had to come.
Therefore, he would rather let Chu Qianli believe that he took the Treasure Map and betrayed her.
This way, at least during this particularly dangerous time, Chu Qianli would not risk saving him.
"Ali, since you've guessed Prince Yexuan's intention, then..."
Some words, Fu Long was uncertain whether to say or not.
Prince Yexuan's return to Beiming is fraught with danger.
Perhaps the Emperor won't kill him yet, keeping Prince Yexuan still has uses.