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I am not sure but I think the following method can be used to "retrieve" all NPCs. But as I've said I haven't tested that.
Note that the text refers to Rimmer but that is not important - this solution has been used for a few different NPCs as well.
Harglowe's missing Rimmer solution: Alas, I turned the dwarven village inside out, but no Rimmer.
I did solve the problem in the end, by cheating however.
I took an old saved game (a game where I hadn't been to the dwarven village at all) and temporarily copied the data.000 file from that saved game to my newest saved game (after making a backup of the original data.000).
It appears that the data.000 file contains the location of all NPC's and even your own location.
I started up the saved game, went to Rimmers house, talked to him (he was standing in his house, a few feet from the entrance), saved the game and restored the data.000 file.
In Your case the save file should contain such a part of the game when You haven't visited Ars Magicana yet.