Have you tried the Android boot menu? While your phone is switched off Press and hold the Power key and the Volume down key. Wait a few seconds and You should see a bunch of information about your device, and Start at the top of the screen. To navigate through the menu options, you use the Volume up and Volume down keys. The Power key is used to make a selection. You can select wipe data/factory reset, this will restart your phone but completely wipe it including the password. Not a problem if you had your phone set to back itself up every night because when you restore it gives you the latest backup to use. However if your phone was setup up before in a way that still requires the password even when factory reset then you have a serious problem. But only you would know that, did you have find my phone set up?