(a) Sayyidah Aishah (may Allah be pleased with her) says: Abu Jahm bin Hudhayfah (may Allah be pleased with him) gave the Messenger of Allah (peace and blessings be upon him) a Syrian sheet as a gift which had some markings on it, and he (peace and blessings be upon him) prayed in it. When he gave the salam ending the prayer, he said: "Return this sheet to Abu Jahm. I looked at its markings during the prayer, and it almost put me to trial."
(b) Imam al-Shafi'i (may Allah have mercy on him) states: We do not know whether he (peace and blessings be upon him) performed the prostration of forgetfulness or not. And Abu Talhah (may Allah be pleased with him) looked at a wall (during the prayer), then mentioned it to the Prophet (peace and blessings be upon him), and we do not know whether he (peace and blessings be upon him) ordered him to perform the prostration of forgetfulness or not.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3872