How can I unlock my screen?

[AC Question]

I set up the fingerprint unlock, which worked fine for months until I went into an AT&T store. When I left the store, my phone was locked... no fingerprint recognition, and it was asking for a password that I never set! When I went to my google account, it wouldn't let me change my password. Grrrr....
I need to remove the pictures before I do a factory reset, but I'd like to see if I can somehow unlock my screen before I take that step.
Any suggestions?

 

[B. Diddy]

Welcome to Android Central! It's probably asking for your backup password that you selected at the time you set up the fingerprint unlock. Whenever you choose fingerprint unlock, you're required to select a backup password (and confirm it), so it must have been done at some point. You don't remember this?