My Freshman prom was awesome, I made a pretty good connection with the girl, but I called her a day later, no response, called her again maybe 2 or 3 days later. Still nothing...If she had a real good time, she'll make it pretty easy to get in touch with her and maybe set something else up in the future. But, if you want my advice, wait at least 2-3 days before calling her and thanking her.