I'm not going to tell my friend that he was being scammed
Why wouldn't you tell your friend about being scammed?
It's not my house and it's not my business.
If you know a friend has been scammed, you should let him know and not hide this useful information from him. If he knows about it, he might be able to get some of the money back.
If someone is getting scammed it's not my business.
But since he is your friend, don't you think you should warn him about anything harmful that is happening to him?