Just the thumb wasn't enough for me, but after 10min smashing the screen with the bottom of my palm, it finally came back to focus.
I also have the problem, that both backlenses are blurry and can't take any sharp pictures anymore.
The problem occured between 20. and 25. July. I am not sure if the last firmware update was around this time.
My current Androidversiob is 13 and the firmware version is 33.0804.2060.142