I tell you the truth. Listen to me.
You cannot expect other people, even-especially-your friends to always do unto you how you would do unto them.
It is not going to happen. If it does, lucky you.
But in general,
It does not happen, especially in certain, extremely specific circumstances.
So save some breath and faith for the things that really matter, like, whether you trust them or not, or whether they are good for you to be around, or, most importantly whether you are taking care of YOURSELF or not.
Your friends are not going to tell you they plan on dating your ex of two years, because they know you are over him. Just because I would do that for a friend, even if I knew they were over him, does not mean my friend will. See? It just does not work like that.
If it does, lucky you.
And, yeah, I recommend you remember when this happens to you that you remember it is not a super big deal...
...but it is okay that it hurts.
Because, in general, it does hurt.
If it does not, you have no idea.