What would cause an lcd screen to get a dark shape in the middle, even
when it's not powered on?

New guy here is installing 'bluetooth' headsets on some of our ip
phones (Mitel 53xx series). Need to take part of the back cover off &
replace it w/ the portion that has the antennae in it, and when he was
doing one, turned the phone back over & discovered a big dark spot that
takes up almost half the lcd screen on the phone.

I'm guessing he got a little western when putting the screw on for the
new back piece and cracked the lcd case in the back or something.

Anyway, slightly over a $300 **** up, whatever happened.