Although it is possible that the family came with the Salzburger Expulsion, do understand that this part of the East Prussia border existed long before that event. Many Germans already lived in East Prussia prior to it.
These maps http://www.angelwind.com/prussia/maps_historical.html
show border changes over time for various parts of Prussia. Those for East Prussia are fairly consistent over hundreds of years from the earliest settlements of the Teutonic Knights. Since Lithuania was under Russia rule at the time, there would be no immediate connection between Lithuania and the Salzburger Expulsion. Later on of course further migration could have taken place. It seems that there was, over time, significant cross border migration between Lithuanians, Germans, and Poles in this northeast corner of modern Poland, referred to as Russian Poland through most of the 19th century.
Examination in particular of wedding and death records for the region will give you clues about previous origins of your people.