Most of the coffee bags I am familiar with are made from laminated films....polyester/foil/polyester/polyethylene. The foil is very thin and supported by the polyester layers, the polyethylene forms the seals...and has a fairly low melting point.

I cannot imagine these holding up in a fire....boiling food in the bag maybe but not as a cook pot exposed to direct flame.

There must be some sort of coffee package that I have not seen.