I did two Evaluate Bridge Officer Doff Missions, and one did not provide the Boff. I believe the reason is that my Boff inventory was full after accepting the first Boff reward, but the system did not warn me or stop me from claiming the second one. I tried to see if it was hidden by accepting a Boff to my open bridge slot, but nothing appeared. The normal Boff reward system does not allow you to complet a mission if you don't have space on your roster, the same should occur when completing a Doff mission for a Boff and you do not have the required space.
Mystery Solved - The Boff appeared as an icon in my inventory, so it was not lost.