It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that he said: "Two men of the Ansar learnt a surah which the Messenger of Allah (peace and blessings be upon him) had taught them, and they used to recite it (in their prayers). One night they both stood (in prayer) to recite that surah, but they could not recite a single letter of it. In the morning they came to the Messenger of Allah (peace and blessings be upon him) and mentioned it to him, and the Messenger of Allah (peace and blessings be upon him) said: 'It is among what has been abrogated and caused to be forgotten, so leave it now.' Imam al-Zuhri (may Allah have mercy on him) used to read the verse "Whatever verse We abrogate or cause to be forgotten" as nunsiha, with a dammah on the nun and without doubling."
Imam al-Tabarani (may Allah have mercy on him) said: "Only Sulayman bin Arqam (may Allah have mercy on him) narrated this hadith from Imam al-Zuhri (may Allah have mercy on him), and Abbas bin Fadl (may Allah have mercy on him) is alone in narrating it from him."
Hadith Referenceالمعجم الأوسط / باب العين / 4637
Hadith Gradingمحدثین:إسناده ضعيف جدًّا، فيه سليمان بن أرقم متروك
Hadith Takhrij«قال الهيثمي: فيه سليمان بن أرقم وهو متروك «مجمع الزوائد ومنبع الفوائد، ج 7، ص 154»» «أخرجه الطبراني فى «الكبير» برقم: 13141»