Before we look for the missing verses, one must know the history of Quran from Sahih al-Bukhari 4986, how it was gathered.
From this one may note that, all the Quranic verses are not by-hearted by Muslims but was rather written in many things. Else, Zaid bin Thabit won't need to do sooo much hard work to collect it. See that shifting a mountain is very easy for them than to collect it.
Now let's start looking other sources...
In Sahih Muslim 1452a, it says that Allah allows adult breast feeding 10 times which was abrogated and was replaced by five sucklings.
And this Sahih hadith says that Muslims used to recite a Quran which contains breast feeding of adults five times.
When we read the arabic, we can see that the Translation is completely wrong in sunnah.com, they try to save their Islam. "and the Messenger of Allaah (peace and blessings of Allaah be upon him) died while they were reading from the Qur'aan.", This is the correct translation.
In the below image I have translated the arabic. you can see that after the first abrogation of 10 sucklings by five sucklings, Muhammad died. So after that, how can Allah abrogate these without Muhammad. Isn't he the last prophet for Muslims?
So how is this Quranic verse is not present in today's Quran? Because the Quranic verse got eaten by a simple goat, not even Allah couldn't preserve these ayah's from Quran. Read Hasan hadith Sunan Ibn Majah 1944 and this hadith is classified as Sahih by Ibn Hazm (classical scholar | fatwa 12905) but it is classified as Hasan by al-Albani.
One may argue that the two verses mentioned above were abrogated later by Allah. But where is that? If Allah is the one who abrogated that verses through his words, where is his words about that in Quran? How can Allah abrogate the verses after the death of Muhammad? Also, can anyone skip writing the abrogated verses from Quran? If it's possible why are there so much of abrogated verses that we can see in Quran today.
Now look at this Sahih Muslim 1691a it mentions the same thing.
Note that they were afraid that in future people will say these verses are not in the Book of Allah which Muhammad and after that the Sahabis practised.
And one may think that this is before Muhammad's death so that Allah abrogated this verse. For them let's read this LONG hadith Sahih al-Bukhari 6830 from this we can see that this happened after Muhammad's death and it was happened when Umar was chosen as Caliph; i.e after Muhammad's death.
Now, we can say that his fear become real and now we cannot see the verse of Rajam in Quran. i.e means it is missing while the Muslims used to recite and practise it after the death of Muhammad.
If Muhammad is dead, through who will Allah abrogate these ayahs?
Now let's see some other hadith regarding these Soorat al-Ahzaab was as long as Soorat al-Baqarah, then most of it was abrogated - Islam Question & Answer (islamqa.info)
So from this Sahih hadith by Abdullah the son of Imam Ahmad in Zawaa’id al-Musnad (21207) we can see that the surah al-ahzab is a long surah and was about the length of the longest Surah now in the Quran which is al-Baqra. And al-Ahzab was the surah in which verses of stoning was contained.
Note that one of the speaker in the hadith is confirmed that there are more Quranic verses in al-Ahzab similar to al-Baqra and he is didn't even know how this is missing in the Quran.
We can also see this in a Sahih hadith Sahih Muslim 1050
Eventhough, one can claim that the second surah forgotten only by the Sahabi and that verses can be found in 61:2 and 17:13. But what about the Surah which is LONG as al-Baqra? You will not find any surah which as long as al-Baqra in Quran today.
And we can say that the verses in al-Ahzab got missing. How? A tame sheep ate it.
No body can prove that these ayahs has abrogated, there is no eveidence for it, instead it was eaten by a tame sheep. Is that how it should be abrogated by a goat? Who can abrogate the verses in Quran? Allah right? Why isn't that in Quran then?