Where mutual affection is involved and the man is sensitive in the way he proceeds, children tend to maintain their silence and discovery is difficult.
Not only in consensual relations the disclosure is usually unwanted by the child. In some abusive relations the child wants only to stop the sex, but doesn't want to see the adult in jail.
But after the authorities become suspicious, it is hard for a child to remain silent against the adults around him.
Results from Sorensen & Snow 1991 give some illustration: 74% unwanted disclosure (i.e. 14% by sexualised behaviour). If the children have told, then in 72% only after denying at first. 22% have later removed their accusations, but 98% of these later told that their previous accusations have been true. Bradley & Wood 1996 give completely different numbers: denial only in 6%, recantation in 4% of the cases.
Because it is easy to find out from the police records, there are a lot of statistics about the discovery (source: Brongersma 1990, p.35, 146).
Albrecht 1964, p.272, from trial records: 57.6% child's parents, 16.7% police, 6.1% eye witnesses, 4.6% youth protection authorities, 3% each of collegues of the accused, mother of another child, neighbours, school staff, 1.5% each of the child himself or his brother.
Gerbener, in Duisburg (N=515): 45.0% child telling sombody, 8% police becomes suspicious, 35% observation by wittness, 4% implication by other child.
Niemann, in Hamburg (N=354): 58.5% child telling sombody, 16.4% police becomes suspicious, 12.4% observation by wittness, 12.4% implication by other child, 0.3% adult blackmailed to make confession.
Nabel, (N=787) quoted by Geisler 1959, p.63: 40.0% child telling sombody, 37.0% observation by wittness.
Baurmann (N=8053): 7.5% police becomes suspicious, 12.0% the minor, 54.6% the parents, 10.4% a neighbour, 2.4% youth protection authorities, 4.6% school. 8.5% other.
Wolters 1982, p. 74 (N=106) (children 3-11 years): 1 case by child, 85 cases by parents, 6 by neighbours, 5 by official agencies, 4 by other children, 4 by other family members.
See also Rossman about 17 American cases.