Can't remove a fingerprint scanner prank

[AC Question]

So I downloaded this fingerprint scanner prank on my s6 edge just to play around and later I decided to delete it. After I deleted it, I turned my device off and when I turned it on again, the fingerprint scanner thingy was still there. I checked again if I deleted it and sure enough, it was. I really need help cuz this is rlly annoying. Oh and does rooting my device help the problem? Its currently running marshmallow 6.0.1 without root