I'm with Ruby on this, there is no way of knowing if he did do it.
If we delved into the realms of probabilities and statistics its far more likely for a woman to be raped and not report it than for a woman to falsely accuse a man of rape. Although neither are unlikely to be possibilities here.
What does need reviewing is the whole way rapes are dealt with. Some years back my friend suffered one of the worst rapes I have ever heard of. She was attacked walking from school to the church. She was found unconcious and battered beyond recognition, despite the overwhelming evidence her life was still put on display for everyone to see, her dirty laundry was aired and she was made to feel like the guilty party to some extent. Given the choice to be able not to, I would never report a rape, if it happened to me but maybe my opinions would change over years. How long ago it may or may not have happened should have no bearing on the matter.
If he has done nothing then I feel incredibly sorry for the man but if he has the woman stands literally no chance of getting him convicted as lets face it, the chances of getting any rape allegation tried and convicted is nigh on impossible.