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I think that you have to understand why these people deleted your links. A) Are they reading Matt Cutts and worrked that he is going to slap them for linking to you? B) Are you posting things on your site that they don't like? C) Did you competitor contact them and say something that made them take down your links. D) Do they think that their site looks better without links to other websites. E) Are they afraid of losing traffic to you or leaking linkjuice. F) Some other crazy idea in their head. So, maybe the first action would be to get in touch with them to find out why the links were taken down...  This would be a hard message to write but maybe you could ask if you did something to offend them and were writing to see if that was the reason.