Ship stuff aside, I honestly think she called Nick. Nothing romantic at the time, just friends hanging out. I mean, it makes sense considering she was heeding his advice. I would say that TPTB said at the time that people were supposed to assume it was Nick so they didn't bother to say who it was, but we know I'm a canon fan and frown upon depending upon commentary, so I won't rely on that.
Seriously, though, I don't think it was Hank because that scene in
The Finger was supposed to be their first date (at least i thought it was). It certainly wasn't Grissom because I don't think they are comfortable enough with one another to go out anyway (plus, Grissom isn't very social). She and Catherine have never really gotten along well enough with one another to go out alone like that. That leaves Warrick, Nick, and Greg. Considering Nick made the comment (to which she listened -- as she always does to his advice
), I think it is most logical that she called him.
Either that or that scene in
The Finger wasn't her first date with HankSkank and she called him.