YouTube video with AudioJungle watermark on

I follow a YouTube video and noticed on one of his videos the AudioJungle watermark during some music that he was using.

What are the rules on this?

I get annoyed at people who promote themselves as being professional but seem to steal music!

The rule is you can’t use the preview on a published video. However, it does not necessarily means that the music was stolen. Indeed many editors work with the preview before final validation by their customer, and some of them simply forget to swap for the actual track, even though it was correctly licensed.