Any drop to cause the lcd to break will show damage on housing. Any pressure to crack LCD will crack housing plastic lcd protector. A Crack LCD WILL still show back light. you will see the crack on lcd once turn on. But OP say no display. This is bad LCD and under warranty. I never seen a Crack LCD with LED backlight without Backlight.
I bet the service guy cracked it when opening the camera and blame it on the user.