U mean the rumor that their "probe" which touched before the US one, had single cosmonaut onboard. But it hit to hard and killed him, and they never made the claim public because he failed to get a message off or return to earth.
Also a rumor that in orbit above the Earth are a # of 1 way Soviet Doomsday Weapons, consisting of a single cosmonaut with a Nuke, designed to be launched downward if we went to Nuclear Hot. In theory a # of the "dark" space mission were design to recover these and bring them home. Also there maybe manned anti-satelite platforms.
Or that they made a mistake on 1 reentry attempt and sent a cosmonaut or more on a 1 way trip to the sun.