First time poster/longtime reader...
Scene of the lost ticket appears to be in Germany...notice the sign in German.
While everyone has probably made this deduction, yes, that is the DB reservation office in the Hamburg Hautbahnhof. I was just in there booking a train trip a month ago. It is just inside the entrance seen in the other photo, to the right when you walk in. Very cool to see a place I've been so recently featured, even if it is just en route.
19 Euros is too cheap for a ticket to Belgium. It either says a higher amount, or it could just be a reservation, as some trains require seat reservations, while others do not.