I'm having the same issue, although I don't remember doing an update. I have Sprint, and an OS update did come through OTA a few days ago.
I went to log into my phone, and the fingerprint scanner just wasn't there. Nothing I did was able to bring it up, and the password I thought I had isn't working.
I tried using Android Device Manager to reset it, as some folks have suggested, but when I locked the screen, it told me that it successfully locked the screen, and then that was followed by a brief message that ADM has detected that the screen is already locked so I won't need the new password.
I really don't want to lose the configuration of my phone because I finally got it all organized on the home screens with apps in folders and the like, and I have around 200 apps I have on my phone (it's a royal PITA to re-install them all as I have four devices and not all the apps I have install, and some apps from other devices install, so I have to manually go through and uninstall and then try to remember which apps I wanted to install, blah blah blah).
What's going on here? I'm really disappointed; this is the first issue I've had with the fingerprint scanner and I really like it because (a) I don't use my thumb and (b) it's just a lot quicker to log in than a password or PIN and (c) no one can see the pin/passcode/lock pattern if they're watching me on the phone.
Ugh!
