Food science questions on Getbig are never quick but the quick answer is no: the protein remains.
Example: when you cook scrambled eggs, the water which is held in suspension by the proteins is expelled as the proteins denature or 'uncoil.' That's why the pan sizzles - the expelled water is being forced out of the eggs (along with the mechanical pressure of heat turning the water to steam) and onto the hot pan. It's also why egg emulsions like Hollandaise sauce will fail at a temperature which denatures the protein complex in the yolks. So the protein complex is altered by heat but none of this makes protein disappear. It's just reorganized. (And fwiw you will utilize more protein from cooked eggs than from raw ones. Raw eggs are not the way to go for a few reasons.)
I can't see why cooking a piece of meat would do away with protein either. The only loss I can possibly see would be from the maillard browning on the outside, but even then I'm not sure if the aminos disappear or not and you'd have similar browning on a rare or medium piece of meat.
But only a rube would overcook a good steak.
