According to new YouTube policies and explosion of YouTube "claims", it will be extremely unlikely to have uncredited actual copyrighted songs as soundtrack of YouTube videos. Indeed, if a YouTube creator uses a copyrighted song for a video soundtrack, all incomes are lost.
When someone asks to identify a song which is soundtrack of a video from a YouTuber, two cases can most likely occur:
YouTuber uses a song from YouTube Audio Library. So unless someone volunteers to listen to thousands of songs to find the good one, I suggest to close the question and suggest OP, in the comments, to go to YouTube Audio Library website.
YouTuber uses a copyrighted song (and accepts to lose all potential incomes) and the song is credited in the comments. Close the question for lack of research and suggest OP to check the credits of the video.
I don't see any reason to keep these questions open.