I found my self in a similar situation, opened up Nova launcher, got to the widget part, activities, setup wizard then I somehow placed on my home page, I then removed it, went back to my activities widget only to find setup wizard gone. I did want to pull out my hair, but thank God for you, you don't have to, you don't even need to reset your phone, you've merely disabled the system app,all you have to do to enable it is this, go to
Settings
Apps
Then tap on your top right hand side ":" to get a drop down menu(depends on the phone you have anyway) where one of the options will be "show system" tap on that, your system files will then be visible scroll down and find setup wizard tap on that and enable it and voila.