We do not know of anyone who reported anything to support what 'Amr bin Yahya said about praying on a donkey. As for the Hadith of Yahya bin Sa'eed from Anas, what is correct is that it is Mawquf. And Allah knows best.

That is a saying or action of a Companion of the Prophet (ﷺ)
Sunan an-Nasa'i Book 8, Hadith 54
← Previous Hadith "I saw the Messenger of Allah (ﷺ) praying on a donkey, when he was heading toward Khaibar."

Sunan an-Nasa'i Book 8, Hadith 53 Next Hadith → Al Bara bin Azib said: The messenger of Allah (peace be upon him) came to Al-Madinah and prayed toward Bait-al-Maqdis for sixteen months, then he was commanded to pray toward the Ka'bah. A man who had prayed with the prophet (peace be upon him)passed by some of the Ansar and said: "I bear witness that the messenger of Allah (peace be upon him) has been commanded to face toward the Ka'bah. So they turned to face the Ka'bah".

Sunan an-Nasa'i Book 9, Hadith 1