I can't find anything mediawise that explained the loss.
However, I have spoken to my vLove, who says David was crying during his match with Schuettler in Dubai. And Javi was there. He (my vLove) is convinced that these tears were emotional and that something's happened in his personal life - he suggested a breakup with a gf or a loved one's death - but that he's chosen not to speak to the press about it.
Whatever it is, what doesn't kill you makes you stronger David!