I'm not to suave with the lingo but I can say: empathize with her. You found some common ground which happened to be video games (not exactly raunchy). Then you had to leave without giving any speciifics of hints to make her even remotely curious. It was all very abrupt and the asking for the number was random in context; it would have been more appropriate asking for it around the times you were talking about clubs, dinner, etc.
Give her a reason to feel content about giving her number to you. Also, you gave your number to her which I would say is a big no no. That is basically saying "please call me sometime because I like hearing from you." (needy)
But all is not lost. Online conversations are abundant and arbitrary and this won't leave a major battle wound, just a scab (beautiful metaphor
). Next time obey a few of the common daytime game rules. Question her interests and find a more interesting common ground. Make fun of some of her qualities in a cutesy manner. push/pull...impress her with a dhv routine(plenty on this site that can be used online), make her want to talk to you...roleplay a date even, and then in a subtle manner, almost covert, ask for her number, Ex. "I closed the window last time before you gave me your number."