Ata (may Allah have mercy on him) narrates from Abdullah bin Abbas and Ibn al-Zubayr (may Allah be pleased with them both) that both of them said, concerning a woman who has taken khul' and whose husband then divorces her: Divorce does not apply to her, because he has divorced what he does not own.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14866
Al-Shafi'i (may Allah have mercy on him) said: I asked him, meaning one of those who differ with him on this issue, whether he narrates any report in support of his view. He mentioned a hadith by the like of which no proof is established, neither with us nor with him. I said: This, with us and with you, is not established. He said: Some of the Tabi'in held this view (al-Shafi'i named the two of them in the Book of Judgment by Oath together with a Witness): al-Sha'bi and Ibrahim al-Nakha'i. Al-Shafi'i said: I said to him: And the view of some of the Tabi'in is, in your own opinion, no proof, even if no one else contradicted them.
The Shaykh (al-Bayhaqi) said: As for the report that was mentioned to him, its chain has not yet reached us so that we might examine it; I searched for it in many books compiled on hadith and did not find it. Perhaps he meant what is narrated from Faraj bin Fadalah with his chain from Abu al-Darda' as his own saying, and Faraj bin Fadalah is da'if (weak) in hadith; or what is narrated from an unknown man from al-Dahhak bin Muzahim from Ibn Mas'ud as his own saying, and that is munqati' (broken) and weak.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 14867