Justin Timberlake's new music video for "Not a Bad Thing" debuted on his friend Ellen DeGeneres's show on Thursday, and it's a documentary-style video looking for a real-life couple who got engaged on a New York train using Justin's song. The backstory? On Jan. 12, a man proposed while playing "Not a Bad Thing" on a train heading to NYC, and two documentary filmmakers heard their story and set out to find them. A voice-over in the music video says, "They were so in love — you almost never see that. We don't know who these people are or what their story is, but maybe you do." The filmmakers put up fliers all over NYC with the hashtag #haveyouseenthiscouple, and the music video itself is now a search for the mystery pair. Following the video's premiere, Ellen said, "Obviously, if you know this couple, contact us, because Justin is trying to find you and we'll put you all together." Watch the full video above.