For the last couple of days my phone has been kind of a pain to work with. I would use the keyboard to type something in, and either the entirely wrong letters would show up, or nothing at all. Last night I got around to grabbing an app off the Play Store to show where touch events were detected and then turned on the developer options that do pretty much the same thing.
I rebooted my phone, I rebooted my phone into safe mode, nothing helped.
This is a screenshot using the app I downloaded. I basically ran my finger all over the screen, and I noticed this area where nothing showed up.
So then I tried it with the developer options turned on.
That dead area makes my phone pretty much unusable. Thankfully my phone is still under warranty, and I'll be able to send it in and get a replacement. In the mean time I am charging up my Nexus 6 and will transfer my number back to it so that I have a working phone until the replacement arrives.