If you are writing documentation then you don't want to use an assigned magic number, like a real IP address or a real DNS name. That can readily lead to: misunderstandings; operational difficulties for the vendor's equipment if the number escapes from documentation into production; and difficulties for the author because of the risk of defamation and trademark infringement.
For these reasons standards associations commonly issue a range of their magic numbers for documentation purposes. For example, the IETF issued magic numbers for documentation in RFC2606 for DNS names, in RFC5737 for IPv4 addresses and in RFC3849 for IPv6 addresses.
I was writing some documentation for using udev, and rather than defame some vendor by suggesting that their product may need a workaround, I asked the USB Implementors' Forum if there is a USB Vendor ID for documentation purposes.
Sadly, there is not:
From: USB-IF Administration <redacted>
Subject: RE: Vendor-ID for use in documentation
Date: 11 November 2014 2:34:21 PM ACDT
To: Glen Turner <redacted>
Thank you for your message. Vendor IDs (VIDs) are owned by the vendor company and are assigned and maintained by the USB-IF only. We do not have a generic VID for documentation.