Sauté onion, celery, garlic, parsley, and thyme in butter in a large Dutch oven until vegetables are tender. Gradually add half-and-half, stirring constantly.
Drain oysters, reserving liquid. Add liquid to vegetable mixture; heat thoroughly without boiling. Stir in oysters, sherry, salt, pepper, Worcestershire sauce, and hot sauce. Continue cooking over low heat, stirring constantly, until mixture is heated and oyster edges curl. Serve warm.