That would probably be due to the dns propagation, there's usually a brief delay before a new domain is fully known over the Internet.
If you visited the site on your computer before propagation had reached your ISP, that would stick in cache for a bit. Eventually it would have cleared on its own, when the cache expired.
The reason you saw it directly on the phone was likely that when you got around to testing there, the propagation had already completed for the service provider you use on your phone, and since you hadn't checked prior there was no cache serving the faulty error.