Does "This day We shall save you in your body, that you may be a sign to those who come after you" refer to a divine miracle unrelated to the science of mummification, or did the pharaohs possess a science of mummification that perished due to their concealment of it?

It is well-known that Allah Almighty brought Pharaoh's corpse to Musa so that the Children of Israel could verify his death. This was one of Allah's miracles, confirming Musa's message. Some of the Children of Israel doubted Pharaoh's death, so Allah commanded the sea to cast him out with his body intact, soulless, and with his famous armor, onto a high place, so they could be certain of his death and destruction. Allah Almighty's bringing out of Pharaoh's corpse and displaying it to Musa's people has no relation to mummification, and there is no evidence to prove his corpse was mummified. Some scholars doubt that the body currently found in Egyptian antiquities is the corpse of the Pharaoh of Musa.