It says in the article that Szeth was not bonded with a spren, but I believe he was at the end his chapter in Words of Radiance. He was given the black sword, and a voice talked to him from it. I think that voice was supposed to be his spren.
Have you not yet read Warbreaker by Brandon Sanderson? In this novel, the 'Awakened' (i.e.: 'sentient') sword, Nightblood is wielded by Vasher. Once Vasher is relieved of this sword (likely by Nale, potentially through Hoid), it is ultimately possessed by Nale, who gifts it to Szeth upon his revival from death (by Kaladin).