Originally Posted by
Concerto
A DB counter agent once told me that it is possible to upgrade a saver ticket to the normal price by paying the fare difference, so the ticket is not totally lost. But you have to find an agent who is willing and competent enough to it. That you will certainly NOT find at Düsseldorf airport, that counter is dreadful and really sucks,,a disgrace to DB. But Duisburg or Düsseldorf main station would do it, I reckon.
Every Sparpreis Ticket can be used on a later train against payment of the fare difference plus a service fee of IIRC 15 Euro. This can also be done onboard long distance trains (ICE, EC, IC). And as it is a hassle for the conductor to do, many may be willing to let you ride with your existing ticket if you describe the circumstances (5 out of 5 for me so far...).