I was just in an awkward social situation the other day where someone left their phone on a table at a party and walked away to do something. Some guy was telling an interesting story and we were all trying to politely listen, but suddenly that phone started ringing at full volume. Everyone just kind of ignored it at first but it kept ringing. I was annoyed and wanted to reach over and mute/end the call, but, you don’t touch other people’s phones in polite society. Eventually it stopped ringing. Amazingly, everyone just acted like it wasn’t there. I guess we’ve all become accustomed to such things.
In my circles, you would mute the disruptive call with the side button and tell them, “sorry, your phone was ringing while you were gone and I muted it.” Or just “your phone rang while you were gone.”