I knew there was a bug in this since I got bit by it once before. If you miss a day, the next time you log in it will say you still have the consecutive days in the UI, but if you click the number you can see that you really don't.
See the image below, it says 14 consecutive, but I've missed Sat and Sun (currently Sunday here, but not in UTC time).
Edit: This is really by design to display incorrect results? Here is another shot of the UI this morning when I logged in.