I believe there was a hiccup with the version you got stuck with. In that version, the update-check failed to see newer versions.
When you’re at home, you had been using the locally installed version of Plex Web. When away from home you accessed Plex through http://app.plex.tv/desktop (the hosted/online version of Plex Web). The online version recognized that your server wasn’t up-to-date, the local version didn’t.
Over time you might have noticed that the look & feel got a little different 
If you don’t want to miss future updates you can bookmark the release announcement thread (using the “bookmark” button at the end of the respective thread in the forum; not the browser bookmark feature). This way you should get e-mail notifications when there’s a new release and what’s in it.
That being said… the current version of Plex Web will also show you what’s new when it indicates there’s a new version of the Plex Media Server.
