Combine the flour, thyme, 1/4 teaspoon salt, and black pepper in a large zip-top plastic bag. Add the shrimp; seal and shake well. Heat olive oil in a large nonstick skillet over medium-high heat. Add the shrimp, and sauté 3 minutes. Remove shrimp from pan. Add onion, bell pepper, and garlic; sauté 2 minutes. Add sherry; cook 1 minute. Add 1/4 teaspoon salt and tomatoes; cook 4 minutes. Stir in shrimp and vinegar.