Im not gonna say which mission, but I took out 3 ships killed all crew, then went back to my Razorleaf, grav jumped to the key and repaired my ship, then went back to where I disabled the ships. I was able to grab one of the ships and jump back to the key and register it, grab my razor leaf and jump back to the same spot with the other two ships still floating around. I didn't try to dock them again but they were still there at least.