Hit him back and/or hire people do it. In the future, a good part of CF that farmers usually do is post confirmation of CF both ways on both walls. Example: FARMEE (on farmer's wall): I accept CF terms and have paid them. FARMER (on farmee's wall): CF granted. That way there is public proof of a CF being paid, and even if one deletes the other and tries to back out there's still the other wall post as proof. I'm sure a farmee can suggest this. If your farmer doesn't like the sound of that confirmation, then that would be a red flag imo and you probably shouldn't pay CF.
I ask people to post on my alt's wall so I know who has CF terms set up with me or CnC. But yeah anyways pay me and I'll farm his RS (Did I forget to say he has fairy stats?)