I never heard of it before either, but now that I look, it is on the list of breeds recognized on the American Bantam Association website. Neat!They reasonably conform to the ABA standards for the Red Junglefowl bantam, a breed I’ve never heard anyone talk about before.
https://www.bantamclub.com/recognized-breed-and-variety
The American Bantam Association recognizes a breed called "Junglefowl" in a color called "red." So yes, a breed by that name DOES exist, and is clearly the one OP means ("ABA standards for the Red Junglefowl bantam" cannot reasonably refer to anything else.)Red Junglefowl do not exist anymore so the RJF bantam cannot exist either.