I'm not sure if this is a bug or not. It probably isn't, but I don't like to post a bunch of whining and complaining threads, so I'll post it once here and if this strikes you as something you'd like to change...it would make me happy.
I notice that finding a magic site does not keep that magic site in the computer's memory of what you know.
For instance, if I find a site then lose a province, that magic site doesn't show up anywhere in the province information. I contend that you should still be able to see it.
If I send a spy and notice a magic site while spying, this knowledge disappears when the spy moves from one site to another. I would think that my "master of spies" would keep this information stored somewhere.
Not as critical but also interesting is that the gold income and population of a province is no longer known once your dominion no longer touches it and you no longer control it. Granted that this number will vary, but it would be nice to at least see "Last known values." Of course, I have no way to know how difficult this would be to program, and it might make the savegame files somewhat larger, though I doubt the latter will be much of a problem.
Also, one Last matter, it seems the barbarian horde pillages and reduces your province's population even if it is conquered by your patrolling troops. Do they not get there in time to prevent catastrophe? Or am I imagining this result?