Harkness stayed with River, out of the way, not wanting to go back right then. Donna could handle his human. Hopefully.

The Doctor didn't startle until he heard Donna call out to him, and he jerked, lifting his head and turning to look at her with wide and wild eyes. "Donna..." No, no... This isn't... He can't have her here, not right now. "Sorry. Bit busy," he told her, with some fool's hope that it would be enough to send her away. Of course, it didn't help that the things he had been "busy with" were now a wreck on the floor.