Feather dusters drop their "feathers" for seemingly unknown specifics but it is sometimes due to stress and sometimes thought to be a reproductive means (just what I heard at LFS).
Yes they are known to abandon a casing and start a new one if something isn't just right. Give it time and odds are you will see it has secreted a new home in a few weeks.
If you touched it and it didn't move that's NOT a good sign. When mine came out of it's casing even disturbing the tank would aggitate it to move and show signs of life.
good luck.
Allen
