Just adding my two cents.......
As far as we know Umar ra knew it was abrogated, but what planet is silent killer on, Saying Umar ra never knew it was abrogated?
Hajar Al Asqalani says in his commentary on Saheeh Bukhari...
Umar said: "When this verse came down I approached the Prophet peace be upon him so I asked him: Should I write it down?' It is as if he hated that" Then Umar said: "Cant you see that if the old man if he commits adultery he does not get the whip, and that if the young man if he commits adultery he gets stoned?" (Ibn Hajar Al Asqalani, Fathul Bari, Kitab: Al Hudood, Bab: Al I'tiraaf bil Zina, Commentary on Hadith no. 6327, Source)
Here we clearly see that the Prophet (peace be upon him) did not want the verse to be written down because it was never meant to be part of the text of the Quran. The scholars of Islam are unanimous that the recitation of this verse has been abrogated but its ruling still remains in effect.
However, the only reason why Umar got emotional and wanted to put the verse in the Quran was because he was afraid that one day people would think that its ruling had been cancelled. However, the companions did not allow him to because they all knew that its recitation had been abrogated. In order to put a verse in the Quran there needed to be two witnesses and Umar was all by himself. Umar himself knew that its RECITATION WAS ABROGATEDbut he was getting emotional, for he feared that people in the future would not believe in the ruling of stoning the adulterers.
Imam ibn Hajar Al Asqalani has in his commentary...
In the verse whose recitation has been abrogated but its ruling remained, and it has happened what Umar feared. A tribe from the Khawarij or most of them and some of the Mu'tazilites rejected the stoning.
And it was reported by Abd al Razzaq and Al Tabari from another view that Ibn Abbas said that Umar said "There will come a people that will lie (or disbelieve) in the stoning" (Ibn Hajar Al Asqalani, Fathul Bari, Kitab: Al Hudood, Bab: Rajam Al Hublah min Zana Eezha Ahsanat, Commentary on Hadith no. 6328, Source)
Imam Nawawi says in his commentary in Saheeh Muslim...
Muhammad Shams al-Haqq al-Adhim Abadi, Awn al-Mabud Sharh Sunan Abu Dawud, Kitab: Al Hudood, Bab: Fil Rajam, Commentary on Hadith no. 3835, Source)
And the companions of the Prophet abandoning the writing of this verse is clear evidence that the abrogated should not be written in the Quran and that Umar's statement about the stoning as he is on the pulpit and the silence of the companions and other than them from who were present from opposing him is evidence about the ruling of the stoning (still being implemented) (Imam Nawawi, Sharh Saheeh Muslim, Kitab: Al Hudood, Bab: Rajam Al Thayb fil Zina, Commentary on Hadith no. 3201, Source)
Al Sindi says in his commentary on Sunan Ibn Majah...
The verse of stoning: Its recitation has been abrogated and its ruling still remains in effect. (Al Sindi, Sharh Sunan Ibn Majah, Kitab: Al Hudood, Bab: Al Rajam, Commentary on Hadith no. 2543, Source)
Muhammad Shams al-Haqq al-Adhim Abadi says in his commentary on Sunan Abu Dawud...
And this is whose recitation has been abrogated but ruling remains in effect. (Muhammad Shams al-Haqq al-Adhim Abadi, Awn al-Mabud Sharh Sunan Abu Dawud, Kitab: Al Hudood, Bab: Fil Rajam, Commentary on Hadith no. 3835, Source)
We can clearly see that there was a consensus amongst the companions of the Prophet (peace be upon him) and the scholars that the recitation of the verse on stoning was abrogated and that they did not corrupt it. How can all the companions of the Prophet (peace be upon him) who sacrificed everything they had for this religion just happen to decide to come together and purposely corrupt the Quran by removing this verse? What motive would they have in doing so if its law was to remain being implemented? So there can't be a motive to remove this verse simply because they wished to not follow its ruling since the ruling still remains in effect up to this day.
So clearly the evidence shows that this recitation was always meant to be abrogated while its ruling remains in effect.
And ALLAH SWT knows best