I have entered a weird state
Firefox was open. The icon appears in the cmd+tab task menu.
In the dock it shows as "not responding". Force Quit does nothing though.

Ok... but then it doesn't show in Activity Monitor either. I have searched for "Firefox", "fox", "ff", "mozilla" and skimmed through by eye.
I have also tried grepping the output of ps aux and top in terminal but I can't find it.
I wondered if maybe it wasn't really open and just the dock icon/task switcher were confused, but when I double-click Firefox from the Applications folder:

I have tried relaunching Finder but it doesn't fix anything.
I assume a reboot will fix it, can anyone suggest another avenue?
topornettop– Anentropic May 26 '15 at 20:12launchservicesdfrom Activity Monitor gave me an eternal beachball of death, hard to hard boot the laptop. – Anentropic May 26 '15 at 20:21