Have you ever owned land? If so, when you purchased it were you advised about “adverse possession”? If not, how exactly were you supposed to know it existed? Were you supposed to divine it?
You don't need to know about the doctrine to know that people are trespassing on your land. If the "owners" would have commenced an ejectment action against the judge during the twenty years during which the judge had openly used the property, then this wouldn't have been an issue, would it?
Ignorance of the law is why real estate courses are offered at the local college. It will all be explained and those who skip the opportunity need not worry about the real world—the world of law will make its presence known.