We get something like this in Appalachian ballads and other isolated (Anglo)American folk musics recorded in the 20s. Little attention was payed to American folk music until the early students of English ballads discovered 100+ year old tunes (thought dead to oral tradition) in tact due to the isolation of the mountain valleys. They were the most preserved versions of those songs in existence.Their singers had no concept of them being passed down from anywhere but their home but they likely had melodies and rhythms in common with the broadsides of their grandparents homeland.
https://www.loc.gov/collections/songs-of-america/articles-an...I've noticed a similar thing where blues music fans are unaware a tune they consider "traditional" is actually a version of a published minstrel show tune. It seems pop music doesn't die, we just forget where it came from until it becomes folk music. Then I guess we forget that happened and try and make it up the melodies from scratch.