You can try retrieving the data from the Backup Folder using the Notezilla Troubleshooter app.
To change the master password, click on "Forgot Password" link from Advanced tab of Notezilla Preferences. To access Notezilla 's Preferences, right click on Notezilla icon and choose Preferences from the menu.
If you use the new master password on an existing locked note, you will still not be able to get the content of the note (unlock) since the password for that particular note is different. The note will unlock, but the content will not be readable/understandable.
Unfortunately, it is not possible to open a locked sticky note without it's master password.