GoldCircle: So, I visited GZ - and found the cache missing; unfortunately, I found a hypodermic needle also, so, sadly, this location is no longer suitable for hiding caches and I decided not to replace the cache.
I looked around for the trackable logged to the cache, but no obvious sign - I'll return in winter when the grass is lower.
The Puzzle:
The symbols on the main image on the puzzle page were a decoy - they could be resolved to a set of coordinates nearby, where a brick was hidden with a note commiserating with with the unlucky cacher. The real puzzle was contained on the cache page background wallpaper - it was an "Aztec" Code - a type of scannable code that looks very much like a QR code - however, you need an Aztec scanner to release the coordinates.