[sangnoir]

I'm specifically referring to the Google Maps mobile app - it doesn't have a search bar, but has buttons that come and go depending on your current context. If a button is visible in your context, you can bet it works in that context. As an example, the layer, compass and search buttons are present when you're not navigating, but once you start, the layer and compass buttons are replaced by the audio chatiness button. The search button is still present, and the implication is that its usable in my current context: that's great discoverability in my book.