Silesia is still on the maps, but the german Silesians were ethnical cleansed or emigrated later and the population had been exchanged with those from eastern Poland which became Russia/Ukraine.

And what happened to the germanized poles?

Another problem that Polish authorities were faced with was the disposition of the so-called "Germanized Poles" or "autochthons". Of close to three million residents of Masuria (Masurs), Pomerania (Kashubians) and Upper Silesia (Silesians) of Slavic descent, many did not identify with Polish nationality, were either bilingual or spoke German or Germanized dialects only.