Sphagnum moss can be found in the plant section of most stores. If you paid more than $3 a bag you got snookered.
I use it for my orchids. Since I started planting my orchids in moss instead of bark I have not lost a single plant. They will need watering a lot less frequently and I don’t have the mildew problems that I sometimes had with bark.
I use this for my carnivorous plants as well. The bog plants love to grow in the sphagnum moss.
And most importantly I use it for rescue plants. When I have a plant in trouble I plant in in wet sphagnum moss and use a clear plastic bag to create a greenhouse over the plant. That along with a bit of fertilizer with rooting hormones will bring back just about any plant from death’s door.