The Kitáb-i-Aqdas
9.We have set forth the details of obligatory prayer in another Tablet.   ¶8
The original Obligatory Prayer had “for reasons of wisdom” been revealed by Bahá’u’lláh in a separate Tablet (Q&A 63). It was not released to the believers in His lifetime, having been superseded by the three Obligatory Prayers now in use.
Shortly after the Ascension of Bahá’u’lláh, the text of this prayer, along with a number of other Tablets, was stolen by Muḥammad-‘Alí, the Arch-breaker of His Covenant.