The author of this puzzle provided you with a series of letters followed by arrows that were pointing up and either to the left or right. It could be a substitution cipher, but not very many letters repeat, and the one that does (A) has a different arrow beside it the second time. That makes substitution unlikely. So how do you figure it out?
The description provides a wealth of clues. The CO says that the idea came to him as he was writing a cache log and used the phrase "I followed the arrow all the way to the top." So we know that the arrows are important, and that we need to 'follow' them. But follow where?
The second big clue is in the first sentence "I was sitting here staring at my keyboard." All the letters appear on a keyboard of course. If you look you will see that the keyboard can be divided into diagonal rows that either lean to the left or two the right, just like the arrows. This code uses those diagonal rows to encode.
The second half of that first sentence in the description gives you the final piece, "all the way to the top." What is at the top of a keyboard? Numbers!
Here are two letters and how they encode the numbers above them:
So what do you find at the final location? A giant arrow!
The arrow is a marker for the "Quanah Parker Trail," a history trail that flows through all 52 counties of the Texas Plains Region, honoring the last chief of the Comanche who led his people prior to their being sequestered on reservations.
There are more than 70 (!!) of these arrows all over the Texas Panhandle to mark areas of local history, and locations where Quanah Parker and his tribe hunted, traded, lived, traveled, and fought.
How did you do with the puzzle?