Frontier Airlines EarlyReturns (Pre-Alignment) - Flight #63 to PVR from DEN exist?

I called Early Returns to check availability to PVR, and they claim on 11/19, there are 2 flights available. One flight at 9:35AM, flight #69 which I can see on their website, and other booking engines, but they claim there is a 2nd flight #63 departing at 1:05PM from DEN. Anyone can explain this anomaly? Does this flight actually exist?