It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that "the Messenger of Allah (peace and blessings be upon him) had a thread by which he (peace and blessings be upon him) would remember (something)."
No one narrated this hadith from Abd al-Hamid bin Ja'far (may Allah have mercy on him) except Hushaym (may Allah have mercy on him), and Abu Ma'mar (may Allah have mercy on him) is alone in narrating it.
Hadith Referenceالمعجم الأوسط / باب الميم / 7156
Hadith Takhrij«أخرجه ابن حجر فى «المطالب العالية» برقم: 3044»