Amr bin Asim (may Allah have mercy on him) mentioned it in the same way, except that he narrates that he (peace and blessings be upon him) said: "Whoever has not prayed the two rak'ahs of Fajr, let him pray them after the sun has risen."
Amr bin Asim is alone in narrating it, and Allah Almighty knows best; and Amr bin Asim is thiqah (trustworthy).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4556