I recently saw a new report about these stickers. They are meant to be able to return lost paddle boats that may have gone adrift. By putting your information on the sticker, hopefully your boat will be returned. It also prevents the Coast Guard from looking for a person(s) if only the boat went adrift. They can immediately call the number on the sticker to see if someone is or is not missing.
You can pick one up at the Dauphin Island Coast Guard Station from the watch standers between 0800-1600 (8 a.m. to 4 p.m.). I would imagine that the one in Gulf Shores also has them.