You lost 10 points from the downvote in Main. Moving, deleting, or doing anything to a post doesn't change karma gained or lost from it, and votes on posts are worth 10 points in Main.
The other 10 might be another downvote in Main before you moved, though that's a narrow time window.
This seems like [edit:] an undesirable feature in this case.
http://www.sciencedirect.com/science/article/pii/S1053811911006008