Musannaf Ibn Abi Shayba 3:3189

Ibn ‘Ulayyah narrated to us, from Yunus, who said: A man was asked about a person who performed two rak'ahs on Friday, but was unable to perform the prostrations until the Imam had performed the taslim. He said: I was informed regarding al-Hasan that he said: He should perform two prostrations, then stand up and complete the first rak'ah.