I think there should be something on the letterboxing website where if
you are logged in, you can say that you have found one and keep track
of the boxes you have found. Geocaching has it. I placed one sort of
far from me and the only way to see if anyone has found it or make
sure it is ok is to go there but I can't very often. The only problem
is that people might give away the location, but hopefully it wouldn't
happen very often.