Ethnic Germans Found, 'Resettled' Jews Not Found

We now know that, in the post-war USSR, a highly stigmatized ethic German population was still able to be traced by the West German government:

Nearly 2.2 million ethnic Germans have returned to Germany from the Soviet Union since 1950, said Jochen Welt, a high government official whose office is responsible for the immigration and assimilation of ethnic Germans back to Germany.

So why has no-one found those millions of Jews - transported to Auschwitz, Chelmno and the Reinhardt camps - that deniers claim were resettled in Soviet territory?