I have seen the fingerprint option appear sporadically below the numeric keypad. The last time I caught it I set up fingerprint security. After I set it up I used it successfully.
Now it's not there anymore and I haven't seen it come back since. Appears to be some kind of bug. I'm attaching a screenshot of my Settings. Let me know there's anything else you need. This is an iPhone 6S plus. Thanks.
THis would be an Apple issue, not Comcast