It seems there is a problem with the back button when using nested states.
When using an abstract parent state and navigating directly to the child state (like ui-router is supposed to be used, to my understanding), the back button doesn’t show.
I did find a workaround, which is to set the parent state as non abstract, navigate to it instead of the child and in its controller use $state.go to navigate to the child state.
While it works, I still believe this is just a workaround and the issue is a bug in ionic.
I’d be happy to hear Ionic team’s thoughts.
Here is a codepen demonstrating the issue and the workaround: