Chalda
I'm sorry but there isn't a whole lot you can do. I know this is very traumatic for you but online friends are just that. Online friends. When you don't know them it real life you are pretty powerless to help. Support him the best you can but you are going to have to come to terms with the fact that he may be leaving your life. To some people online friends can be just as close as real friends, so whether or not she knows this person is irrelevant.
Anyway, it is much, much harder for children to be taken from their parents than people seem to think.
I have a lot of experience with this situation, and kids generally aren't removed from homes if they don't want to be (if they're old enough to make the decision) and they definitely won't be removed if there isn't any proof.
In fact, the way the system works, kids sometimes aren't even removed if there is proof.
There are so many abused child cases and too few people to handle them, because of this, DCF (department of children and families) or whatever organization that will handle this, won't waste their time removing him from his home without proof.
What will happen is that the report will go on record, someone will probably come to his house to talk about it, and without proof, they will probably give the parents a warning, and they'll leave.
I really don't think you need to worry about it.
You can PM me if you want more details on how the process works, if you'd like.
gonk