Yes, but it was not a flight to the Grand Canyon as you originally wrote, it was even worse: A flight from the Grand Canyon to nowhere (via the Twilight Zone ?).

So I think the people who coded up the $50 charge were sick of their user interface, and just decided to throw you off of the Grand Canyon rim into the Colorado River.

IOTW, I'm presuming that Alaska's system won't process a charge like this without some airport code being put in some field. Perhaps some employee who was not familiar with that just typed something at random and that's how it came out on your statement. In any case, there is nothing to worry about with credit card statements for award redemptions, they virtually never have the right airports on them, no matter who you're redeeming with, because the charges are not actually for the flight, but for the fees, and these fees don't have the itinerary attached to them the way a paid ticket does.

Maybe it wasn't even FLG that they typed? Maybe it was a code for a private airport (that commercial airlines doesn't fly to), and that's why it came out as "Grand Canyon" instead of "FLG" or "Flagstaff"?