you can get the good fluffy NZ sphagnum to regrow..give it enough light and keep it moist..It starts to grow again. In fact the orchids I keep in jars arent as amazing as the moss the grows in them
..The sphagnum has to be bright and fresh and not all dark and dried out like the standard orchid moss you see in stores all over. When you wet it you shouldnt smell anything like ammonia,( I really havent figured out what that smell is yet and ammonia or cat pee is the closest match). If you do its old and probably not going to grow.The sphagnum should smell like wet grass or hay. It will regrow..if not try these peoples out
Hypnum (Fern/Log) Moss Tray | Mountain Moss. if they dont have the moss you want then it hasnt been grown yet.
They sell flats of live sphagnum for about 25 bucks that is If you dont feel like taking the time to grow your own..I think its fun to watch moss grow. you cant smoke it though. Well I guess you could