Oh man, lucky! Could you try triggering it again on the video you saw it on?I've just seen it, I didn't realise people were tracking it down so went straight to the Shenmue youtube page to re-watch it and realised it isn't saved anywhere. Didn't realise it was like gold dust, I'm so sorry guys.
It was randomly in Spanish, but the actual trailer dialog was in English. It's only 30 seconds and can describe what I remember if you want. It also linked me to this website, when I played it. https://shenmue3.deepsilver.com/es....fJQ95AKMZJXzDoo28B3yn3x9FZq9swgxoCcUcQAvD_BwE
There's some footage from the previous trailers, there's a small section of an old woman looking at the mirror, and Ryo says "I need to know why the mirrors are so important that my Father had to die". It ends with Ryo kicking down a door, and it then cuts to Lan Di standing up, but I'm unsure if it's the same scene or just cut to look like it, and Ryo shouts "Fight me!"
If you do, pause it - right click - go to the "stats for nerds" option - and check the Video ID stat. The sequence of letters and numbers on the left are the way to get to the unlisted ad link.
Oh, and yes please for the description. Stick it in a spoiler tag though, just in case.