[SPOILER (possibly)] Lost Item: Yancy/Curtis sidequest in BW2, help?

So I've gotten past the initial part of this quest. I was called by Yancy at all the required places, returned it to her, and registered her in my Xtransceiver.

But now I can't seem to call her again. Bulbapedia says you need to call her 51 times (Really?) before you can trade with her. I've only seen her in my list of callable people once, and it disappeared after I called her. How am I supposed to do this? Are there certain places/times when she's callable? I haven't been able to find a decent guide for this anywhere.