Can't unlock phone because of an untouchable key!

[Android Central Question]

First off, coming from the title; I can't unlock my phone. Not on safe mode, not on normal, nothing. I did indeed drop it today- and there are NO scratches or damages nearby where the keyboard should appear. The only key that doesn't address on my keyboard is Z, whereas S, X, D, A, upper case function, and the comma DOES work. I really don't want to resort towards doing a factory reset, since there's important files that I didn't back up to my SD card. I can't access my phone on my laptop either, since I need to unlock it for that to happen.