Screen wont turn on, but is still fully reactive to touch.

Well the phone was one of my friends and before she gave me it (because her parents just bought her a new phone) It worked just fine until she accidentally dropped it from id say about... 5 feet... something like that (i'm pretty sure she said it had a case on it.) But the screen didn't shatter. And it would still be responsive to touch. But the screen wouldn't light up. She said that there was at one point it did light up, but it was soo faint that she could barely see it.

She said she took it into a Apple store and the guy looked at it and said something about something being severed?

Also, I followed one of the screen replacement guides on this site. And i made sure the first thing I did when I got inside the phone was unplug the battery from the phone. ( And yes I did power the phone down before doing anything to it)

And still, neither the original screen or the replacement screen lights up.

My guess is that maybe one of the ports plugging the screen to the phone may have been damaged when it fell?

Inspect the LCD ribbon connector on the logic board for any signs of bent pins.

Also try shining a flashlight on the screen and look at the phone in angles to see if an image is being displayed on the screen when it is turned on / booted up.

This may very well be a backlight issue where somehow it managed to go bad after the phone was dropped which is rare for it to happen. I suppose there is a higher chance if the LCD display ribbon cable on the original screen was ripped from the drop.

I looked at the phone with a flashlight and I could see it, though it was very dark.

And I'm actually looking at the logic board under a microscope right now. I don't see any bent pins or any overall damage to the sockets. But right next to one of the two sockets you told me to look at (dont know exactly which one it is.) Its the one in the center. If your looking at your phone as if you were to use it normally. just below the bottom right of the center socket on the logic board. (or directly to the left of the center screw that holds the io shield down. There are two tiny parts on the logic board that look to have melted or exploded or something. I'm not entirely sure.

Since the phone displays an image with no backlight then the backlight filter must of blown and needs to be replaced for backlight to work again.

Just curious, was there any screws that were loose or came off at the earpiece area of the old screen when you opened up the phone for the first time?

Well, when I got to moving the earpiece and the camera from the old screen to the new screen. I looked at the io shield and noticed that the top right screw holding it down was totally missing. And also the right pentalobe screw was missing too.

So how would I go about repairing that? Because I'm guessing id need to either try to learn how to microsolder or try to find someone that knows how to. I do think it'd be very fun to learn how to microsolder. I already have a beginner lab microscope my mom got me when I was really young one year for Christmas. (but its nowhere near the magnitude of the one that's suggested.) And my grandmother knows how to solder. (but she mostly does it for stained glass. The smallest scale I know that shes soldered is when she was making solar panels for their cabin.)