Jul 10, 2013 - 5:24 AM
Thanks for the information. That train does not require seat reservations. It's possible to book a seat, but not necessary. In case of Germany I don't know of other ways to book a seat online, other then the site you already tried. If seats have run out there, it just means that there are no more seats available for online booking, but there will still be non-reserved seats. I would recommend to not book in advance, but if you want to you can arrange for it at a staffed station in Switzerland or call 0900 300 300 from within Switzerland.
By the way, there is maintenance work in progress between Hergiswil and Lucerne on August 15, so the last part of your trip will be by a special replacement bus (which is free for train travelers). All in all the trip will take a bit longer.