The Secular Missionary and the Firebrand can both be upgraded at a hefty cost in fate during the Feast of the Exceptional Rose. However, they remain companions and their new stats are not at all noteworthy. If you happen to have either as a companion already then you have basically reached the end of their content (for the time being).
The absence of the event that allowed you to choose them is odd. Perhaps send Failbetter a bug report? Mention as well who would have been your chosen companion, they may deign to help you acquire it.
edited by Owen Wulf on 3/9/2015