Ok, I got it now! If you hide the active track in the Track Pane, and left click in an open area of the PRV, this mini menu appears. It wants you to select the new active track. If you select the track you hid from that little menu, it unhides it. Thanks again icontakt and others who answered. That one has bugged me for a long time.

No problem. Glad I could help. 

That little chooser could be very useful ... just posted a feature request about it, that it allow multiple selection ... but maybe if it is geared to "active" track, multiples can't be used.    It is such a simple and clear chooser, got the name and the color right there, it would be great to add the track number.