Mmkay, this is a bit tricky, but the situation isn't really a classic "rebound".
The rebound feeling is made when a (usually girl) person gets out of a very special relationship. They then feel abandoned, lost, and want the comfort that another relationship will offer.
That's what triggers a rebound. Usually the person will latch on to the first person to ask them out, despertly trying to get back into the old habits of a strong (or, not-so-strong) relationship.
What you're talking about there (-points-) is just plain old dissapointment.
There wasn't any particular amount of loss. No very strong feelings - 'cept maybe anger and dissapointment. All it's done is to clear her list of "possible date-worthies" of that guy.
You may be able to squeeze yourself in there if you're fast and charming anough. Go for it. But don't think that you have some sort of advantage, other than that she'll be a tad more receptive to other guys.