Alright, so he didn't see the end. That makes it infinite? You're the one who's always so quick to bring up vanishing points.
How else would the atmosphere be contained on a Flat Earth?
Undiscovered 100 mile tall Ice Wall?
Celestial Dome?
It's much likelier that the earth is simply a bottom sedimentary layer of the coin shaped universe, where our local area is simply a fraction of the known world, with endless undiscovered fridged lands to the south which lay in perpetual darkness.
The Flat Earth Society has always held that the earth was likely perpetual in nature, extending farther than any distance attainable by man, where temperatures in the pitch black tundra approach zero kelvin. Whomever made the FAQ did not represent the official stance of the Flat Earth Society.
See ENaG, Flat Earth News, and the other Flat Earth Literature for more information about the perpetual plane of the earth.