I agree it's odd that she didn't introduce you to the man. Don't feel paranoid. Maybe instead of asking directly "who was that man in your kitchen last week?" maybe ask in a broader context; "I was wondering what the FDC policey is about other visiting adults in your home during hours of care?" And if she doesn't know then add that you'd personally feel more comfortable knowing what other people were around your child while he was using her FDC service.

I feel that whether children are being cared for in a centre or in FDC they are all entitled to a basic standard of care and this includes what adults they are exposed to. I don't want to worry you any more than you already are but just because it's a family home doesn't make it safe. Statistically that's where children are most likely to be hurt.... in a family home.

I sympathsise with your own childhood experience of abuse and encourage you to follow your instincts.