With regard to Beardown Man I went there recently but had not realised that my cache had been found nearby. It was getting very late and I didn’t have much time to get home, in fact I arrive back in the pitch black anyway. I knew the cache was not where it should have been and I had a quick look round and then placed another. If reb10 is correct, there are indeed 3 containers there, possibly two of mine and a much older one. I will need to return and investigate.
Another possibility is that some caches have not been logged with Groundspeak but with say Open Caching. In this case we may find a cache and assume that it is an old archived one, but is actually live on another system. I don’t think this is true of Beardown Man as I think the log had not been signed recently, at least not until it was mistaken for my cache.