up to two weeks after the loss date (if found) you will find the property at
hauptbahnhof office (review the mentioned thread). after that it's transferred to a central location out of munich.
if this happened again (hopefully not) go directly to any
S-bahn central stations. infrom the controller and provide him with the exact time of existance of that train at certain station, perhaps he can contact the driver of the train to look for the property at the end station.
good luck