So, knowing the location of one of my new caches was 55 feet away from the mystery cache was no help. I still couldn't find it to get the exact coordinates. Which meant I'd have to solve the puzzle.
After some head scratching I came up with some likely coordinates and went looking for the cache.
Alas, my mission failed. I have emailed the cache owner to see if my coordinates were correct and to advise if they were then the cache is likely gone!