This has happened to me few times while making videos, i think it depends on the music group, for me most of my videos now, youtube recognizes the song and sends me an email, you have someone elses work, blah blah blah, nothing needs to be done blah blah blah, sometimes they take it off though, i have found too that if you put a song and youtube recognizes it, you may not be able to watch it with mobile, many people put the song name and artist, and declare its someone elses work, but i dont think it does anything