Kurt hadn't been smiling, and Sam was worried.
At first, he thought it was because of the epic Loft-Battle-Royale-of-2014 between him and Blaine. To Sam, it would be totally understandable to be unhappy after an explosive fight like that with your fiancé (he would know - he was living with Blaine after all, and was regaled with the stories as Blaine slowly immersed himself deeper into Star Wars fanfiction and seemingly endless bowls of ice cream). Yet, even after everything was resolved between the two, after the move out and after the drama of the situation had faded into nothing but a memory, Kurt still wasn't smiling.
When he heard about Russ, the friend of Kurt's and Rachel's neighbor, it made more sense. Sam had known that Blaine had been staying over at the loft more and more frequently with each passing day (and night), but was under the assumption that it was because the two lovers wanted some time alone. After swearing him to secrecy, Blaine revealed these sleepovers were far from the romantic rendezvous he had imagined them to be having- Kurt had been having nightmares.
So when Kurt insisted upon going to the candlelight vigil, Sam was quick to volunteer to go with if only to keep an eye on him. Which he did. Sam watched as Kurt placed the two white roses at the memorial and wondered what he must be feeling. Here he was in New York City, the city of his dreams, where he felt he could be accepted and escape the tortures and abuse he faced in Ohio - only to be confronted with them all over again. In the city that advocated for equality of all persons, that was supposedly so safe and so accepting, until suddenly, it wasn't any of those things anymore. Sam could only imagine how he would feel if someone was going around assaulting people like him or the woman he loved for merely walking home at night. He would have nightmares too. He wonders if one of the roses Kurt places is for himself – a physical representation of remembrance of what he thought he had left behind, or in memoriam of the New York he once knew and cherished so much.
He was there when Blaine got the call from the hospital, attempting to comfort him the best he could while fighting down his own despair and anger at the situation. He meant what he said to Mercedes, that he wished he could kill those people. The people who dared to hurt his friend and to cause all of them such pain in the process. He wasn't at all surprised when Kurt didn't smile when he woke up, because honestly – what was there to smile about?
But after Kurt was released from the hospital and was slowly weaned off of the heavy medication he had been taking, after suffering abuse and bigotry in the worst way imaginable, Kurt slowly began to smile again. It was slight at first, just the smallest upturn at the corner of his mouth whenever he was feeling particularly amused by Blaine's fretting or Burt's antics. But as their small, disjointed New York family raised their glasses to Kurt the night before his mid-winter critique, he smiled a smile Sam hadn't seen in a long time. Suddenly, Sam wasn't so worried anymore. He knew Kurt was going to be okay.