If you message someone privately on Facebook does it come …

Facebook has a “private message” feature (which is the same as “chat” and the Messenger app on your phone). If you used this feature, there is absolutely no way that someone not party to that conversation would have been notified of it. (Messenger does, however, support group conversations, so there’s that small possibility.)

https://www.quora.com/If-you-message-someone-privately-on-Facebook-does-it-come-up-on-every-friends-notifications