Did you get the speeding ticket in Germany or Switzerland? In Germany the fines are much lower and if the effort for the German police or the city is too big to find your correct address they might drop it. Or worst scenario the next time you enter Germany the border officer will take you in custody until you pay your fine. If you did get your speeding ticket in Switzerland where the fines are much higher there is big possibility that they will not give up so quickly and of course should you return to Switzerland and get controlled for example at the airport they will take you in custody until you have payed.

Best chance to quickly solve this issue is that you contact Hertz again and find out which police department in Germany is in charge of your case and contact them directly.