4.5.3 But all my old professors have left! What am I to do??

That’s a pickle, isn’t it? Don’t worry. We’ve been assured by many experts that professors who leave may often be found, alive and well, at other institutions. While you probably shouldn’t get all three recommendations from people who are no longer at your institution, it’s definitely not going to look outrageous or horrible to have one or two from these guys, particularly considering the high turnover in some departments.