The post-1945 border between Poland and the USSR runs fairly close to the Curzon Line proposed after WWI by Lord Curzon. There were some Poles living to the east of that line but most of them would have fled or been expelled in 1945. There’s no benefit to Poland to seek the return of that territory. (Meanwhile a large part of western Poland was German until 1945...the Poles are better off keeping the existing borders although if it were up to me I would split the Kaliningrad oblast between Poland and Lithuania.)
If they are happy with that border it works for me. Kalingrad; Split between Poland and Lithuania sounds good! (They will not be asking me...or anyone else on this thread) to resolve this issue.