Suppose a person took something from someone and now the person is not alive anymore, and has no living Yoresh. How does he return that what he stole? or is it impossible?
This example given by the Torah in נָשׂ֗א , פרק ה and is explained by Hazal that it involves stealing from a convert. It seems that the idea of a born Jew not having any relatives is considered impossible by Hazal (as brought by Rashi). In the case of the convert, the principle value of the stolen item ( or [according to Rambam] the item itself if it is still extant Thank you Alex for that correction!) is paid to the Kohen. Rambam also teaches us that if the principle after being split by the Kohanim of that shift does not amount to a prutah per Kohen then the robber does not fulfill the obligation of returning the stolen item. (Again, thank you Alex!)