Just after we picked up the cache, but before we could open it, a car pulled over behind ours and a voice called out, "Did you find it?" OK.. fellow geocachers. Nope. It was the couple who owned the land the cache is on. The told us that they found out the cache was on their property when they drove by one day to find people walking in the woods near the road.
We were a bit unhappy to find that permission hadn't been granted (or even requested) before the cache was placed. Fortunately the property owners are fine with the cache being there and, if anything, seemed to find the whole thing a but amusing.