Somehiker,
Mitchell's version (and other versions) indicate the Horse/Priest stone was found first. There was considerable (

) time between that discovery and the discovery of the trail stones.
I'm working from memory here but I believe the narrative tells us the Horse stone was found between Christmas and New Years of 1949. Feel free to fill in exact details. Travis took the stone home to study and learn from it. Time passed (weeks to months) as Travis learned and waited for additional vacation time to continue the search. When he returned to ultimately find the trail stones, Arizona was in its hot season. He speaks of the blazing sun, sweat, and heat of the desert. There isn't sufficient time between late December 1949 and end of March 1950 (print date of photo) to take all that in. To me, its a red flag liberty was taken with the time line.