Why did Rebbe Chiya bar Abba imply that he doesn’t know the psukim of the Aseres Hadibros? Could it be that an Amora didn’t know whether it said the word ייטב in the Second Luchos?!
Check Tosfos in Baba Basra 113A (referenced by רע”א and the Mesoras Hashas) who says that indeed they didn’t!
Check the Maharatz Chiyas who says that of course he knew the psukim, but since we find that the first and second Dibros were said at the same time (שמור וזכור בדיבור אחד), therefore he didn’t know if we could really talk about one being first and one being second.
Check the Ben Yehoyada, who also talks about it.
I was thinking (לע”ד) that perhaps we could say that of course Rebbe Chiya knew the psukim, but he just wasn’t sure if it was the type of extra word one could make a drasha from. דיקא נמי from the fact that he sends Rebbe Chanina to Rebbe Tanchum who was an expert in אגדה. He doesn’t say go to an expert in מקרא, rather an expert in אגדה – someone who knows how to darshan!
Check also the Maharsha who clearly does not take the statement literally.