What did I do to the touch screen?

I got a Surface for pretty cheap in order to repair it. It wasn't turning on. I think the volume button was stuck, so it was in perpetual shutdown or something. I worked on the volume button a bit and got the tablet to turn on. It worked for a week or so and then I took it apart again to put another back on it since I broke the corners on the original one. This time, when I turned it back on, the touch screen stopped working. I'm not sure what happened to cause this, but here are some events that happened.

1. I broke the battery ZIF connector like just about everyone who opens theirs up.

2. I dropped a (magnetic) screwdriver on to the back on the inside, near the left top speaker.

3. A part from the side went missing. Looking at the teardown. I guess it's the black plastic piece that goes over the SD card slot. I have no idea where it went, but I put another one on.

4. I left it open overnight and it was also nearby when I was test-soldering the other battery cable.

Any idea why the touch screen might stop functioning? Like, is the inside really sensitive and it could have just kicked it because it was fragile? I also don't think it needs to match its original back (might be a dumb idea) since I put that on and it still didn't work. I'm totally unfamiliar with touch screens. I tried the tactics I've found elsewhere - cleaning the screen, etc (except I can't recalibrate it because it doesn't work). Luckily I have a type cover so I can still use the tablet.