Asking a friend
I think a fun option for this route might be that after they hang out with Rebecca for a while Gary drops the card and they accidentally leave it at her place. She would then either pick it and thinks its Catherine's real ID and decides to return it later or it is accidentally dropped near here desk and she doesn't notice it. Now you already mentioned that she is a comic artist so in order to get some more changes going to Catherine/Quinn you could have her be the kind of person who thinks out loud about what she is going to draw or you could have a friend of hers call her and ask what she's doing and then she would describe what she plans on drawing in her comic, heck if she's a professional you could really just have her editor call her. All of this of course results in seemingly random changes to Catherine/Quinn that he would have to find a way to deal with. I do feel that parts of this plot line are predictable though but I think the random changes could worth it depending on how much fun you have with it.