The resident atty's here can correct me if wrong, but I believe most states require actual evidence of three things in order to bring charges.
Evidence of sexual contact between defendant and victim, evidence that force was used by defendant, and evidence that the victim did not consent.
Is testimony alone considered evidence? I'm as far from being an attorney as one can get, but seems to me there is some DNA involved and likely phone records or even video of the incident. They wouldn't bring a case like this based on testimony alone.