I suspect it got seized, what was the product? Holland to the United Kingdom sounds like it's cannabis so I don't know if customs will bother to follow it up with the United Kingdom. Or it could just be a error in the tracking and it hasn't been scanned into the system when leaving the country, it's strange the vendor hasn't kept in communication tho. You never know it could turn up in a few days time, there is a delay in postal services due to Christmas.