In the case of a stolen lulav, it is bound to the hadas and aravah, and thus undergoes a physical change of sorts. In fact, the bundle is so different it is given a new name called "hoshanah". Clearly it has been picked up by the robber and has left the owner's premises, so a kinyan has been affected. Assuming that the owner gives up hope of getting the object back, then it looks like the robber has taken the lulav into his possession. Therefore, when put together with the other species, it looks like it should be a valid taking. But is it ? Something seems wrong with this. What is the appropriate concept or principle in Jewish law that covers this?
Your wisdom in resolving this is greatly appreciated.
Shalom
Dear Robert,
The Gemara (Sukah 30b) explains that making the bundle (Eged) is not a physical change (Shinui Ma'aseh) (either since it's not required or because it can be reversed).
There is also no name change (Shinui Shem) since it has the name Hoshana from the beginning since it is normally used for Sukos. Also the Kinyan of Ye'ush with changing premises is only if it passes from the robber to a new owner. Therefore there is no valid taking.
All the best,
Reuven Weiner