Assuming this is a ticket issued by Miles and More what previous posters said is correct:
- If you don't show for a flight your ticket still valid up to one year from the date of issue
- They will not rebook to another flight at the airport.
- You would need to call M+M and rebook to another later flight with the same starting and end point. They allow (not sure if also for non status passengers) some limited routing changes, like connecting in MUC vs. FRA. It could be very difficult to find any award space for long periods, especially when you cannot waitlist (since the traveller has no status). Cost 50 Euro
- If it is a One Way or the start of a return then you can refund for a fee of 50 EUR.
This at least is my experience from the last few years of changing these type of tickets.