I feel dumb for not knowing this, but .... what IS that weird little indentation on the left middle side of the Sony xperia z1s? I thought at first it was the volume rocker (I bought it used) and thought "oh well, must've been broken" and have been using on screen volume controls. Next day, I accidentally discovered the volume buttons on the RIGHT side. So what is this little thing on the left side? It looks as if there had been a button there, about as long as the volume rocker, with two tiny silver knob things in it.