Shia Muslims believe in and follow the truth only. The narration you referred to is a fabricated one as leading Sunni Shaikhs including Umar ibn al-Khttab never believed that Mut'ah marriage was prohibited anytime during the life of the Prophet (SAWA). That is why Umar has clearly said about Mut'ah: It was allowed during the time of the Messenger of Allah and I am prohibiting it. ( Musnad Aahmad Ibn Hanbal and Sunan al-Bayhaqi and Saheeh Muslim and many other Sunni sources).
Wassalam.