Hello and welcome,
Sorry that I can not help you here. That’s the first time I read that something like this can happen. but I think it’s related to the threads about that characters got reset in their progress. Sometimes even with losing the ownership of their buildings. Something is going on with the local save files.
Maybe this can help to locate the issue for the devs.
Unfortunately I don’t think there is a way to switch the characters back. But you can use the orb of nergal to recreate your character.
And a good tip from Croms_Faithful in the linked thread is to backup your savefile on usb.
Does this character switch affect any other things of your game? Everything OK with your attributes, knowledge or receipts you learned?
Maybe you switched also one of this stats with the thrall in your wheel?