So I was out of town the past two days. I left the Pro1 powered off and swapped my sim card into my Xperia X instead (which meant I couldn't take pictures, but oh well). When I got home just now, I powered on the Pro1 and the touchscreen is working again! Unfortunately I still have no idea what went wrong, so I don't know how to prevent it from happening again. But hooray, I have my main phone back!