[Butch Cassidy Slept Here]

Lastly I don't think it is unreasonable to expect a return flight

This sounds like Lufthansa either issued you a one-way ticket, when you thought you would get a round-trip, or they stranded you and you had to pay cash for a return flight.

Depending on what kind of documentation you have to support your case you might try Small Claims Court. However you should only file in a state which has an airport that Lufthansa flies to. If you won, and Lufthansa refused to pay the judgement, you would have nothing to attach if you filed in a state they don't fly to. Among other things you will need to have a copy of a statement showing you had sufficient miles for the given award and a copy of Lufthansa's award schedule with a description of each award. Photocopies of your tickets, if you made any, will also help.

You can also try complaining to the European Union ("EU"). But I don't think frequent flyer disputes is a topic covered by their passenger rights legislation. Here is the link to the EU complaint form:

http://ec.europa.eu/europedirect/write_to_us/mailbox/index_en.htm

Again, as I noted in a previous post, airline frequent flyer programs, regardless of the airline, are, in my view, little more than a glorified shell game. Using airline miles to get free hotel stays MIGHT be worthwhile. But even that may be a risky proposition.

Good luck!