@rares, as far as I understand, and during my limited testing on 8.1, the black screen on android means the overall app window context cant be restored, not only for stage3d.
Even if u have a StageText (native EditText on Android) it doesnt render. For me stage quality toggling did not work.
The only way was forcing the app to reinvalidate and repaint the stage, setting the orientation rotated and back (making sure u are not locked to portait or landscape).
Regarding detection phase, reading pixels from a bitmapdata made by starling textures or specific colores quads captures, can run anytime u want, on activation, on intervals, or when video playback finishes.
Sadly, thats the only way i found effective on my tests, terrible UX, but worked ... if it doesnt for ur case, i have no faith that adobe will fix it.