It was unusual that K would not be at the lab for a few days. But he did have his own life and kept his own schedule, though it was still noticeable. After a week of K not coming to the lab, Viktor was officially concerned. Concerned enough that he had gone to K's apartment to find out what was going on. He had concerns most important that K had somehow gotten hurt and since he was so concerned about anyone else being even minorly inconvenienced, maybe he hadn't told anyone else about it?

Outside K's apartment, Viktor knocked a bit more insistently than he usually would if he wasn't already concerned something had happened to K.