It is also NOT a find if the intention is for you to climb a tree, cross a river or puzzle how to open the container. Seeing the cache is not good enough in these circumstances.
I agree that if the log is too wet or the nano has seized up and is impossible to open then it’s valid to claim a find. No pencil is more questionable – although usually accepted – as all cachers should carry a writing implement!
Cache owners are sometimes very grateful if a missing cache is replaced by someone looking and not finding – provided it really is missing. I think it has to be a cache with a very clear description of where it is meant to be so that there can be no mistake that it is really missing and that the replacement is in the correct place!