Coffee bags were definitely around in 1992 (plus or minus a year or so).
I remember being served coffee (in the same sort of stainless steel tea pots that supermarket cafés still serve tea in) during a visit to a rather odd little transport café (which was actually part of someone's private bungalow) in Norfolk. The lady who ran the place was obviously rather proud of using coffee bags (instead of instant coffee), making a point of mentioning it to me and my father.