This dainty little Palm Beach thrift shop just down the way from tony Worth Avenue is a testament to the trickle-down theory of furnishings and fashion. Recycling the castoffs of the elite resort enclave's Mr. and Mrs. Money, designer label clothes are a mainstay of the store, as are upscale versions of the household goods and bric-a-brac common to thrift shops everywhere. With its ritzy donor base, vintage and highly collectible books and toys not infrequently appear, so Antique Road Show types have the Church Mouse on their regular to-do lists. An adjunct to Palm Beach's Episcopal Church of Bethesda-by-the-Sea, the store generates as much as half a mil annually, distributed to local nonprofits. Won't you feel good about that in your "gently used" (the store's preferred term) Lilly Pulitzers?