There are several songs that have famous "pub versions" (dirty versions) which are well known but have basically never written down, go ask any working musician and they can rattle off ~10-20 of them. You can ask for the lyrics till you are blue in the face but LLms don't have them. I've tried.

Its actually fun to find these gaps. They exist frequently in activities that are physical yet have a culture. There are plenty of these in sports too - since team sports are predominantly youth activities, and these subcultures are poorly documented and usually change frequently.