Is it true, that some US and/or British Prisoners of WW II liberated from Red Army never returned home?

Recently ago I got information, that US and British prisoners of ww II captured in Germany and then at first liberated from the Red Army, but not decapitated and transported to USSR Gulags and never returned home. Is that true? What was done respectively not done by their governments to bring them free? Is it possible, that some of them still live in Russia? Any information about their doom available?