Hey Kurly, I noticed you have your music registered with AdRev. When our music is registered, it’s added to YouTube’s AudioSwap library, which means that YouTube users can access our music from a database and swap out the audio on their videos to our AdRev registered music. https://support.google.com/youtube/answer/94316?hl=en-GB
I suspect this is how that user is using your unwatermarked music. You’ll still be getting ad revenue from that video though, so flagging it to be taken down is kind of counterproductive 