Just as a quick update as to what I've ended up doing:
First of all, I've decided to try to go for the adoption path.
Just to clarify...personally, I would ask the next finder to remove it, log their find and log that they removed it. Then I would archive it since you no longer can maintain it.
I've since removed the log above as I realized it wasn't quite what you meant. Someone has also found that cache very recently and I've reached out to see if they might want to adopt the cache.
As for my cache with the NM tag, I've reached out to someone to see if they'd be willing to take care of that one too.
Thanks for all your help, folks. I think I've got it from here.