You know, a large part of analyzing failures is figuring out what's your fault, but sometimes, we forget to define what's NOT your fault. All of us are aware that a rejection can definitely be because of external circumstances. So can acceptance. She could accept just because she got out of a relationship a few minutes ago and wants to forget about it, or just because she's horny. From my perspective of what you've written, it seems that was what it was. She needed someone for the moment, but wasn't looking for anything else. You may have been able to take it further that night, but not later.

If that is indeed the case, then she simply doesn't want anything complicated, and may be in one of those moods again, later. So chill out, don't worry about it for a couple of days, to show her you're not looking for anything more either (for now, of course), and you won't scare her off by being clingy. Then maybe even a 1/2 week to week from now, hit her up again, and suggest you guys hang out. not a date, no dinner or anything, just some sort of light, fun thing. See where it goes...