If you wanted one, you should have opened your gob and asked . They don't do it, maybe they have a drink after. To the muttering you could have replied "really? funny how everyone has their own way of doing things. We tend to have a drink with our meals, mind if I just grab one? Thanks."
I don't think mutterers should be allowed to get away with it, tbh. They mutter and we are supposed to pretend we didn't hear. Feck that! Reply. Call them on it. or say "sorry, didn't quite catch that, what did you say?"