You are steping towards the ridiculous now Stuart. Nobody officially reports anything and the alleged attackers must tell other people about it because that is what they do.
In conclusion, we can assume that the attackers aren't telling enough people, or the right people, about these incidents. It isn't for local people to hope to hear a confession, it's for people who have had such an experience to report it so something can be done. If they won't, then that's all of us waiting for the criminals to boast about it to us, which they do. But so far not to me, or anyone I know.
Nonsense I'm afraid!