Did you open it in a tab that was not immediately made active?

There seems to be some sort of issue with Twitter whereby the javascript to fetch/render the tweet doesn't fire if you open it in a background tab and then visit the tab.

Refreshing the page causes the javascript to correctly fire and the tweet is displayed. This is due to Twitter no longer pre-rendering the page server side, its all done client side.

Also makes it impossible to use Twitter from a browser with javascript disabled.