I don't see that entity on the website.  Possibly that was deliberate.  Is it listed once you do an account or order with them?  You can't lien or attach BTC but does the company have any assets in the US that could be frozen by lis pendens?  Since yufu is in the US the easiest route would be to serve him personally.  He might have been deliberate in publicly stating he doesn't control the BTC sent in but you might be able to depose him under oath to get some answers but the process is very long for that if he fights it.