The usage of "foster dad" and "his child" to me implies that the child was not a foster child. However, foster homes are typically (completely depends on local laws) held to a fairly high bar for safety, so an allegation of neglect against a child (adopted or biological) will be fully investigated.

On the other hand, if it's anything like where I am, then foster parents are at least used to allegations. My wife and I had at least one abuse allegation per year filed against us when we were foster parents. It was somewhat disconcerting the first time. The fifth time, when the social worker showed up it was more "Hi Zoë, how's it going? What's the allegation this time?"