Sony Vegas Media Generators not appearing
The track containing the "hidden" text appears to be muted in the screenshot. Unmute it. It's the icon in the track controls of a round circle with the diagonal.

Background

There are two ways for a track to be muted. First is by enabling the mute switch of that track. This can be undone by clicking the mute switch again. Other is by soloing another track. To solo a track is to show only that track and mute all others. In such a case, the mute switches on the mute tracks won't be enabled but the solo switch on the soloed track will be. All of the other tracks' visibility state "pre-soloing" can be restored by clicking on the activated Solo switch. An additional tip here is that a track muted via solo can be unmuted by clicking its solo switch. This is useful if one wishes to temporarily unmute another track.