In a small bowl, combine the oyster sauce, soy sauce, fish sauce, sriracha, sugar, and water. Mix well and set aside.
Cook the rice noodles according to the package instructions. Drain and set aside.
Season the filet mignon generously with salt and pepper on all sides. Slice it against the grain into small bite-sized pieces.
Heat a large skillet or wok over high heat with a little oil. Once hot, add the steak and cook for 1-2 minutes, or until browned and cooked to your liking. Remove it from the skillet and set aside.
Add the butter and a little oil to the same skillet. Add the lobster meat and cook for 2-3 minutes, stirring occasionally, or until the lobster is opaque and cooked through. Remove it from the skillet and set aside with the steak.
Add a little more oil to the skillet if needed, then add the bell pepper, onion, shiitake mushrooms, and Thai red chili pepper. Cook over medium-high heat for 2-3 minutes, or until the veggies begin to soften.
Stir in the garlic and cook for about 20-30 seconds, or until fragrant.
Add the cooked noodles and prepared sauce to the skillet. Toss everything together until the noodles are completely coated in the sauce.
Add the cooked steak, lobster, and scallions back to the skillet. Toss gently and cook for another 30-60 seconds, just until everything is heated through. Check for seasoning and serve immediately.