ive heard of collecting it because it holds small gold particles and hence the reason we now have "miners moss".
Miners moss is used in the bottom of a sluice box. But, a quick way to prospect a creek to see if it warrants further exploration is to peel the moss off of boulders along the water's edge, put the moss is a 5 gallon bucket full of water and work all the sand out of the moss, then pan the sand. If gold is present in the creek there will usually be several "colours" in the pan. Don't get too exited at this stage of the game though. It can take thousands of colours to make an ounce. Panning moss is mainly just a preliminary exploration tool.
Mark