To find the coordinates for this cache you must complete the Adventure Lab "Slow Down at Rush Ranch". It is not located at the given coordinates. The Lab stops do not need to be done in any particular order.
The tour of Rush Ranch leads you to five locations. You must correctly answer a question at each location to complete the adventure. The final coordinates to this bonus mystery cache will be listed at the end of 2 different lab completions.
Hope you all enjoy Rush Ranch as much as I do!