"Tablet explaining this existed but had been stolen by Covenant-breakers."

The obligatory prayer should be said facing the qiblih (point of adoration, i.e. the direction to face in prayer). The Báb had specified that in prayer believers should face Him Whom God shall make manifest. Thus during His lifetime Bahá'ís prayed facing the person of Bahá'u'lláh. `Abdu'l-Bahá later explained that after Bahá'u'lláh's death, the qiblih was Bahá'u'lláh's shrine and that a Tablet explaining this existed but had been stolen by Covenant-breakers. Facing the qiblih is obligatory for all three obligatory prayers.

John Walbridge, 1950. "Sacred Acts, Sacred Space, Sacred Time." Baha'i Studies 1996