Yeah, I see this all the time with HS students. The way Samsung has the LCD cable ran from the screen to board is not well protected. The body doesn't even need to be really damaged to become pinched in the hinge or under the bezel. Start by removing the bezel and make sure it's following the 'path' underneath. If you can press on the bezel to produce an effect on the screen you'll be able to find where the problem is on the cable. Next I would dissasemble the Chromebook, and try to identify where the cable is being pinched in the hinge. While you're doing that be looking for damage on the cable, it may need to be replaced.
Apply some heat with a heat gun or hair dyer (BE CAREFUL OR YOU'LL WARP THE SPACE BAR!) once the glue is loosened a bit you can apply pressure and slide the trackpad downward away from the keyboard (you'll notice the gap around the trackpad become more distinct) and you should be able to 'click' again.
Hmm, was the power button broken before the touchscreen went out? Sometimes the connectors to the screen come loose. I usually have trouble with the LCD cable, but perhaps the digitizer cable needs to be reseated. Otherwise replacing the front panel on a 4s is cheap and easy enough.