Hi Michael,
I would tend to think that it was really Thompson who was in command.
Is there a date in the discharge book? If it was Hickson, then why is not his name there? Why did the newspapers mention that Thompson was there and spend about 12 hours in a lifeboat? On the other side, there are the newspaper reports mentioned by Mark. Sadly I haven't find anything about Hickson in my stuff yet. [I think the Afric was warned of an possible U-boat in the area and the warning was adressed to Captain Thompson. Will need time to find it.
Unfortunately even with the most famous ships, like Majestic (II) we don't know every Captain! So regarding Afric possibly it was planned to be Hickson to be the captain for that voyage but was then changed for some reason. Would be interesting to find out!