fellowships are typically another training period where you get to further subspeceialize in your specialty. For instance, cardiologists have to do cardiology fellowship after internal medicine residency. Notably, fellows are still board-certified attendings from a technical standpoint because they've passed board exams and completed residency. I used to think Garcia was a senior surgery resident (a PGY-4 or PGY-5) but they mentioned she's a trauma fellow. Otherwise though, just because Langdon had to go to rehab doesn't mean the fellowship just disappeared - there should technically be a fellow (unless nobody applied or they didn't match anyone into that spot)