Replaced display assembly now white bar across the top

Hi,

I replaced an iPhone 4 LCD and now there is a white line across the top? I thought it was a dud LCD so i replaced it again. However the line is still there!

When i initially replaced it i didn't notice a small screw had fallen into the phone upon assembly. When I turned it on it was kind of flickering at me at the top where the white bar has now appeared. I replaced it with new LCD and that's when i noticed the screw had fallen in there.

The screw was located under the board where the gold prongs are that connect the board to the ear piece speaker.

Now I'm not sure if i have cause a hardware fault or anything or if i got the phone originally in this condition and didn't bother to check the LCD before the initial repair. I would love if anybody could offer me any input as Im a bit confused as to what has happened. When I asked the owner of the phone if this white bar was there prior they said it wasn't.

I'm not entirely sure if they are being honest with me or if shave intact shorted something?

Any help would be most appreciated.

Thanks for your time