Making stealth kills with a throwing knife is a common trope in popular culture, from movies like Rambo, 'realistic' spy novels like Jason Bourne to video games like Far Cry 4. Additionally, several sources claim that they were utilized by special forces for similar purposes. The defense website, GlobalSecurity.Org claims that:
The practice of silent killing is an important skill to the spetsnazovets. During the Soviet period, the entrenching tool was commonly seen as the usual weapon of choice for killing an opponent from a distance. The shovel could be thrown or, if close enough, swung, to kill an opponent quickly. Penetration by a sharp entrenching tool spade was usually sufficient to cause severe internal injuries and immediate death. ... ... In the early 1990's, elite troops gradually turned away from the entrenching tool and began to rely more heavily on various specially-designed knives and bayonets. Knife throwing became an important part of the soldier's training in his basic course.
This is further corroborated by the wikipedia page on ballistic knives which cites pg 45-46 of Steve Crawford's "Deadly fighting skills of the world" as saying that Soviet Doctrine emphasized on the use of the thrown knife for making silent kills at 5-6 paces.
I still feel a little skeptical as I can't imagine how this would be possible without the victim screaming. An instantaneous kill seems challenging as well given the protective chest muscle and rib cage surrounding the heart.