This is a bug that got introduced in PT11 where the big counter disappears. I work in film scoring where we display the video on a second monitor with the Bar Beat counter overlaid for the musicians to see.
Here are the steps to reproduce:
1. open a session that has a video track
2. output a movie window to second monitor
3. open big counter and overlay over the movie (I put it in the upper right corner typically)
4. Command TAB to switch to another application and the counter disappears (goes behind the video window). When you switch back to Pro Tools, it's still gone
4a. Another way to make it disappear is to select a single ungrouped audio track in the Edit window then press "CONTROL \" to create a new playlist. When you press Enter to dismiss the window that asks you to name the playlist the counter will disappear.