The Kondo insulator SmB6 is purported to develop into a robust topological insulator at low temperatures, yet there are several puzzling and unexplained physical properties of the insulating bulk. A collaboration with Jeff Sonier from Simon Frasier University reports muon spin rotation measurements of SmB6 that show thermally-activated behavior, confirming that bulk spin excitons may be the source of these anomalies and may also adversely affect the topologically-protected metallic surface states. This work supports the idea that spin excitons play an important role in the anomalous low-temperature bulk properties of SmB6. The manuscript is to appear in NPJ Quantum Materials (2018).