yoinkers: I think this puzzle was just too obscure--definitely an instance where you had to be inside the CO's head--lots of opportunities to get lost in the empty space there! No recent action and moreover, the cache has fallen victim to park district maintenance. No sign of it when I went to inspect the area today. Probably was gone since March per a note from KeeganC. Due to my surgery and convalescence I wasn't able to get out much before now to check out the situation.
I may re-use the puzzle with a different location of course, but for now this one is archived. Thanks to everyone who participated.
goinkers