As a former Child Protection Social Worker, child neglect and abuse was something I routinely assessed for. Having professional experience to draw from helps, but when you do not, it can be a bewildering experience for any parent. The articles below are helpful guides on assisting parents with what questions to ask your child and why keeping ‘secrets’ can be tricky.
http://denver.citymomsblog.com/parenting/why-we-dont-keep-secrets-in-our-house/