The Aquarian Gospel of Jesus the Christ was “channeled” in 1908 by a chap named Levi Dowling. One part of it describes Jesus’s trip to India where he gets into a debate with a Buddhist priest. The Buddhist argues in favor of the theory of evolution, while JC refutes it, and actually uses the phrase “survival of the fittest”.
In the late 19th century, there arose in Panjab the sect of Islam called Ahmadiyya which based part of its theology on Jesus having lived in Kashmir where he died of old age. AFAICT this sect was the first to start popularizing the idea of “Isa” (Jesus) living in India. The Ahmadiyya had begun proselytizing in America about the time Levi Dowling was “channeling,” so it’s possible he might have heard of the idea they disseminated either directly or indirectly.
Holger Kersten’s book Jesus Lived in India traces the origin of this theme to 1887 when a traveler supposedly heard it in Kashmir from a Buddhist monk. My surmise is that the story was actually put out by Ahmadiyya missionaries in support of their claims. They were trying to establish a heterodox sect within Islam and win converts from regular Islam. By claiming that Jesus was buried in India, they meant to deny his Ascension and therefore deny the Parousia. Orthodox Muslims, like Christians, believe in the Ascension and Parousia of Christ. The Ahmadiyya were attacking both at once.