The question is...how did you detect them?
How does Chess.com detetect INCONSISTENT cheaters

I think they should have some sort of report system in place. There's this guy, I crushed him and then he rematched and I suspect cheated on me. I can't remember his username... renummoratedfrog or something and then some numbers.

From http://support.chess.com/Knowledgebase/Article/View/124/0/cheaters--cheating-what-you-need-to-know :
Note also that, to keep our regular forums free of a subject that tends to cause unnecessary anxiety, we have created a special forum thread for discussions of cheating in online chess. Please restrict your comments on the subject (if any!) to that forum. Thank you!
http://www.chess.com/groups/home/cheating-forum
These are the players who cheat only some of the time, for example, when they just lost a game and they were challenged to a rematch....