Did the Prophet (peace be upon him) say, "غفرانك (Your forgiveness)" three times, along with three light taps on the forehead, after finishing in the lavatory?

Ahmad, Abu Dawud, Al-Tirmidhi, and others narrated from Aisha that when the Prophet, peace and blessings be upon him, exited the lavatory, he would say: "Ghufranak (Your forgiveness)." In Sunan Al-Bayhaqi, there is an addition: "Ghufranak, Rabbana, wa ilaykal-masir (Your forgiveness, our Lord, and to You is the ultimate return)." The addition mentioned in the question, of repeating it three times or striking the forehead, has not been reported with an authentic chain of narration.