I liaise with the Forestry Commission Dorset, and used to do so with the FC New Forest too, regarding our agreements with them. Occasionally someone would point out a new cache that had slipped through the system without permission. I always contacted the owner, and all but one of them were extremely apologetic and co-operative, and all got retrospective permission even though some had to change their containers or move the cache to a different nearby hiding place.
Just one owner was a real PITA, but I myself got retrospective permission for him anyway.
Do not go gentle into that good night.
Rage, rage against the dying of the light. (Dylan Thomas)