Reported ‘Aisha (RA): ‘the verse of stoning and of suckling an adult ten times was revealed, and they were (written) on a paper and kept under my pillow. When the Messenger of Allah (PBUH) expired and we were occupied by his death, a goat entered and ate away the paper.’ (Sunan Ibn Majah, Hadith 1944)(See also, Musnad Ahmad 6/269 Hadith 26359, if you don't like the chain of narration in Sunan Ibn Majah)
Notice the following about that hadith.
1) Shortly after Mohamed's death, a goat came into Aisha's sleeping area and ate the paper that she had placed under her pillow.
2) The paper had "the verse" on it.
3) This verse was about (a) stoning and (b) suckling an adult ten times.
While the Koran that the Muslims have today mentions stoning, there is no verse regarding suckling an adult ten times, much less any verse about both together (both suckling and stoning).
Sometimes the authenticity of the above hadith is challenged. Perhaps more needs to be said about that, but it is not the only relevant hadith.
Here is another hadith that has more attestation (these three ahadith are related, as you will see):
'A'isha (Allah be pleased with, her) reported that it had been revealed in the Holy Qur'an that ten clear sucklings make the marriage unlawful, then it was abrogated (and substituted) by five sucklings and Allah's Apostle (may peace be upon him) died and it was before that time (found) in the Holy Qur'an (and recited by the Muslims). (Sahih Muslim, Book #008, Hadith #3421)Notice that in these accounts, it is again stated that the "ten sucklings" were in the Qur'an. There is a claim that this was then abrogated in favor of five sucklings.
'Amra reported that she heard 'A'isha (Allah he pleased with her) discussing fosterage which (makes marriage) unlawful; and she ('A'isha) said: There was revealed in the Holy Qur'an ten clear sucklings, and then five clear (sucklings). (Sahih Muslim, Book #008, Hadith #3422)
Yahya related to me from Malik from Abdullah ibn Abi Bakr ibn Hazm from Amra bint Abd ar-Rahman that A'isha, the wife of the Prophet, may Allah bless him and grant him peace, said, "Amongst what was sent down of the Qur'an was 'ten known sucklings make haram' - then it was abrogated by 'five known sucklings'. When the Messenger of Allah, may Allah bless him and grant him peace, died, it was what is now recited of the Qur'an." Yahya said that Malik said, "One does not act on this." (Malik's Muwatta, Book #30, Hadith #30.3.17)
But there is more!
Yahya related to me from Malik from Nafi that Salim ibn Abdullah ibn Umar informed him that A'isha umm al-muminin sent him away while he was being nursed to her sister Umm Kulthum bint Abi Bakr as-Siddiq and said, "suckle him ten times so that he can come in to see me." Salim said, "Umm Kulthum nursed me three times and then fell ill, so that she only nursed me three times. I could not go in to see A'isha because Umm Kulthum did not finish for me the ten times." (Malik's Muwatta, Book #30, Hadith #30.1.7)
Yahya related to me from Malik from Nafi that Safiyya bint Abi Ubayd told him that Hafsa, umm al-muminin, sent Asim ibn Abdullah ibn Sad to her sister Fatima bint Umar ibn al-Khattab for her to suckle him ten times so that he could come in to see her. She did it, so he used to come in to see her. (Malik's Muwatta, Book #30, Hadith #30.1.8)
This seems to be an example of the application of the "ten sucklings" principle. Why would Aisha suggest that an adult go be suckled ten times? Doing so would, in her mind, make the person a foster relative. And a foster relative (while prohibited from marriage) would be permitted to see her unveiled.
It seems clear that all this testimony provided above regarding the missing verse of the Qur'an is linked back to Aisha. Was she lying or mistaken? Perhaps she was. If Muslims want to insist she was lying or mistaken, how can I prove she was telling the truth?
On the other hand, why assume Aisha was lying? From a historical standpoint, is there any record of anyone challenging Aisha's claim during her lifetime? She was one of Muhammad's wives. If she was lying, wouldn't one of Muhammad's companions be able to say so and have that testimony preserved amongst the ahadith?
In short, why isn't the above historical evidence - as such - credible? Do you accept that your Koran is short at least one verse, or do you reject that idea based on presuppositions that have nothing to do with history?
P.S. Incidentally, there is at least one attempted Muslim response to the issues above (example). That response relies on questioning the authenticity of the narration. However, the response is honest enough to admit that there is an alternate chain of narration that does not have the flaw above. Moreover, the response highlights the existence of other narrations with different words (presumably referring to some of the second category I identified above). These other narrations, however, just highlight the problem.
Secondly, the response suggests that Mohammed said that the verse about stoning couldn't be written. It's not clear what this is supposed to prove. It seems to further support the idea that the written Qur'an is not complete.
Thirdly, the response points out that in some of the narrations, the verse is described as abrogated. However, why should the abrogated verse be omitted from the Koran?
The response's conclusion is even more puzzlingly odd:
Moreover ‘Aisha (RA) lived through the whole period of Qur’an compilation during the time of Abu Bakr (RA) and Usman (RA) while she was unanimously considered an authority for herself so if she had any thought about some verses missing she would have brought it to attention of other Companions of the Prophet (PBUH). Infact we have evidence of Usman (RA) making special endeavor of consulting ‘Aisha (RA) and her records for verifying the official compilation. See Ibn Shabba’s Tarikh Al-Madina p.997. Despite all this she never raised the issue supporting our conclusion that no part of the Qur’an was lost even if the narration is considered reliable.What is odd is that the respondent thinks this helps his case. Aisha is deemed by Usman as a reliable authority on the Qur'an during the period of compilation, yet her uncontested testimony is that part of the Qur'an was lost. To say she "never raised the issue" begs the question at best - more to the point there is a record of her raising the issue, and supporting evidence that she really believed it to have been revealed, or at least really claimed to believe it to have been revealed. Her testimony also explains why she couldn't hand over the verse to Usman during the period of compilation.