Corban's department had been checking for any trace of Umbridge's magic since they were able to calm the immediate area down enough to find out who it was that attacked the notorious Madam Dolohov. So far there hadn't been any pings on their magical radar indicating where she might have gone. The consensus in his department was that she was simply laying low for the time being. Eventually she would get sloppy and start using magic again. When she did, they would find her and make her answer for the attack.