Killing map boss let extra Content disappear.

Last map I first killed all rares, than I went to the boss with the intention to finish the map first before doing the extra content (in my case Expediton + Brach).

I died once to the boss and took the 2nd portal to finish him.

But after killing the boss all the extra content was gone and I wasn't able to do it.

Also the whole map was undiscovered and remeaning monster count was 0 after entering the 2nd portal....before the whole map was discovered and the remaining monster count was 46.