If you are building an object and "shift + left mouse click" anywhere on the map, then the city info panel goes away, although the build menu is up.
I'm not sure if this is intended feature or if it was unintended.
I would point out that this goes a long way in building a city, but in order to bring back the city info panel back you need to be done building. I would prefer a hot-key to remove the UI and still keep building, that same hotkey bring back the UI instead of this current "feature". See pic.
