(a) A similar hadith is also narrated through another chain, but in it is: "We used to pray with the Messenger of Allah (peace and blessings be upon him) in intense heat, and one of us would take pebbles in his hand; when they had cooled, he would put them down and prostrate on them."
(b) Shaykh Abu Bakr (may Allah have mercy on him) says that these are two hadiths narrated by Bishr bin al-Mufaddal, one of them about the garment and the other about the pebbles.
(c) Imam al-Bayhaqi (may Allah have mercy on him) says: What is narrated from the Prophet (peace and blessings be upon him) about prostrating on the fold of the turban is not established; rather, what is sound on this matter is what is reported from al-Hasan al-Basri (may Allah have mercy on him), which is the practice of the Companions of the Messenger of Allah (peace and blessings be upon him) (may Allah be pleased with them).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2666