According to Discovery News, via Marmot:
Photographed intact by Harry Burton (1879-1940) during Howard Carter's excavation of Tut's tomb in 1922, the royal penis was reported missing in 1968, when British scientist Ronald Harrison took a series of X-rays of the mummy.
Speculation abounded that the penis had been stolen and sold.
"Instead, it has always been there. I found it during the CT scan last year, when the mummy was lifted. It lay loose in the sand around the king's body. It was mummified," Zahi Hawass, chief of Egypt's Supreme Council of Antiquities, told Discovery News.