All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
This Hadeeth was not narrated by Al-Bukhari and Muslim, as you mentioned and it is not found in the books of Sunnah. Ibn Taymiyyah, said that this Hadeeth is unknown, and that only the Raafidhah (extreme Shee’ah) mention it.
The Saheeh Hadeeth on this topic is the one indicating that if a Muslim dies without making a Bay‘ah (pledge of allegiance to the Caliph/Imaam), then he would die a death of Jaahiliyyah, and Muslim narrated this Hadeeth.
And Allaah Knows best.