sure it does. If there using different a different isp, the 'home' isp could still be routing them to the old site.
I guess it's also a possibility that the 'home' isp caches pages for faster browsing and hasn't updated that site yet in their cache. I helped do a site for a church once, and when we moved the site from their isp's server to another, people using that isp only saw the old site. We eventually had to call the isp to tell them to fix it.