Re: Sunny Day
First off, you can let it relearn Sunny Day by either the TM which you find in the Burned Slab or by going to Fallarbor Town and giving the Move Relearner a Heart Scale.
About the Beauty Scarf, you must get your Beauty rating to just about Max, then go to Slateport and see the Fan Club Director. If it's Beauty is high enough, you'll get the scarf.
Phantoms Live Forever, They Just Like To Disappear For A While