Jim, first, I want to refer you to three maps: Map 1 shows Germany as it was from its unification under Bismarck in 1871 until 1918. You'll see the Kingdom of Prussia (in German: Preussen) and its provinces, and in the east you will see the province of Posen -- (Lobsens is in the northeastern part of the province). You will also see how large Prussia was. It stretched all the way from East Prussia in the northeast to and including the Rhineland in the west! That was a distance of some 800 miles! Berlin was the capital of both Germany and of Prussia. Map 2 shows Germany's territorial losses following World War I. Those territorial losses included the Prussian province of Posen, which became part of the newly independent Poland. Map 3 shows Germany and its states today, a number of the new states resulting from the post World War II break-up of the state of Prussia.
Map 1: www.rootsweb.com/~wggerman/map/germanempire.htm
Map 2: www.rootsweb.com/~wggerman/map/germany1920.htm
Map 3: www.rootsweb.com/~wggerman/state.htm
As to Map 3: Following World War II, almost all of Germany lying east of the Oder and Neisse Rivers was given to Poland (except for the northern half of the Prussian province of East Prussia, which was taken by the Soviet Union). The 12 million German inhabitants of eastern Germany were thereupon expelled from their homes under horrific conditions. The Polish authorities then repopulated these territories with Poles.
The province of Posen fell to Prussia as a result of the three Partitions of Poland (1772, 1793 and 1795), when Poland was divided up among Prussia, Austria and Russia and disappeared as an independent country for almost 125 years. The population of the province of Posen was always majority Polish but had a very large German minority. A large part of the German population of the former Prussian province of Posen left after 1918 because they didn't want to live in Poland. Those Germans who didn't leave, got caught up in the general expulsion of the eastern German population in 1945/46. (The province of Posen had briefly belonged to Germany again from 1939 to 1945.) So if you do have relatives in Germany today, there's really no telling where in Germany they might live. Prill is a rather common name in Germany.
Needless to say, all the cities, towns and villages have Polish names today: The city of Posen, which until 1918 was the capital of the province of Posen, has the Polish name Poznan. Lobsens has the Polish name Lobzenica.
You might find the following website useful:www.genealogienetz.de/reg/POS/posen_e.html
Hope this has been of some help to you. (By the way, was the family Catholic or Protestant?)