Captured Beast not appearing in Menagerie

I captured a Saqawine Retch in a toxic sewers map, I saw Einhar pull it into the menagerie and everything. As I have never had a headhunter, the chance at one was exciting so I went to my menagerie (I ported back to my hideout and went from the waypoint there) only to discover the retch was not there. It wasn't in the cage and did not show up in the blood altar unique belt recipe.

I went back to the map and spoke to Einhar and the visit menagerie speaking option was not there.

An important note, I was capturing the soul of Arachnoxia at the time. I had already killed the spider and the soul was sitting in the map device.

Normally I wouldn't have even noticed this, but it was a Saqawine Retch so I intended to beastcraft immediately.