As a general rule, we only post a single DNF for a cache which we can not find, even if we return and search a number of times. We first posted a DNF for this cache a year ago. Found the tool and had an idea of what to look for but blanked. Dino Duo, who had found it, saw our DNF and swung past to see if it was still there, they reported all was good. I came back solo another time last fall and again this spring. I even got the micro maven to crank up her walker and give me a hand last month. Finally, I emailed the Duo and begged them to give me a hand in person to help me overcome my Churinga nemesis. They came over today but, although they had spotted it twice before, apparently became infected by a case of BWB blindness and this time drew a blank.
I've tried the best I could so I guess this one will just have to go on my ignore list.