Your explanation works as well as anyone else's for me.
The dead bodies of the family were burned and then acid was poured on what was left so that there would be absolutely no vestige of the Romanoffs left.
There were rumors that a daughter, Anastasia, escaped, but Anastasia never showed up anywhere else.
Come to think of it, one of the lyrics from "Sympathy for the Devil" where it got around to the Bolshevik revolution was "Anastasia screamed in vain."
Communists were murdering bastards then and they still are now.
Hell say and do anything to gain power. And, the media will cover his tracks by remaining silent. Liberal white guilt and abject stupidity might get him elected.