GUI program vanished from both Desktops/Task Bar, but still in Process list, not in Tree

edit

I had Firefox running, then (possibly) as a result of a key combination I don't recall, it quickly vanished from screen and Task Bar/Window List.

ps ax | grep firefox returns the below+the unneeded grep firefox line (Both ps and the GUI Task Manager, show firefox with seemingly unchanging RSS, VM-SIZE and 0% CPU usage):

johndoe      1916 36.6 14.0 923772 504372 tty1    Sl   13:30  12:15 firefox

pstree | grep firefox returns:

init─┬─2*[ROX-Filer───firefox───25*[{firefox}]]

Questions:

1. How can I tell if (as I understand is possible) the program has been detached from the GUI, but is still running?

   a. If this is the case, how can I try and reattach this process, to at least save my work?

2. How can I tell if the program is instead just "Not responding"?

3. What logs can be consulted, if any, for A) When/How/details of (something like) 1. happened?, B) Keystrokes that caused (something like) 1.?, and C) Why a program closed?