If I look for a cache and don't find it it's a DNF.
If I look for it later and find it, it's a new Found log.
If I DNF (without any one finding it after my DNF) and CO confirms cache is not there I alter my DNF to a note and say why I've changed from DNF to note.
For me, a DNF means I couldn't find what was there and it's a challenge for me to go back and find it. If it wasn't there when I went to look for it...well...that's a bit more of a challenge than I want I like to know my find to DNF ratio.