Whilst I can't say that I would favour doing what the OP did in the first place (how can we expect airline customer service to improve if we keep wasting their time with refunds for tickets that we knew we weren't going to use?), the OP wasn't doing anything illegal. I found the "Hausordnung" on the Unique website and couldn't find anything mentioned regarding what the OP did.

http://www.unique.ch/dokumente/ZRH_hausordnung_E.pdf

However, in the Airport Operating Regulations (only in German I am afraid), Article 98 clearly states that a person buying or acquiring a ticket without the intention of flying is not entitled to access the security/airside area (translated freely, not exactly).

http://www.unique.ch/dokumente/BR%20...01_02_2005.pdf

Do I think that the CSR was overzealous in doing what she did? Not particularly. In this day and age such people are sensitized towards seeing suspicious behaviour. In Europe we are still a long way off from the paranoid behaviour we see in some parts of the world, but if the CSR felt that the OP might have had more nefarious reasons for doing what he did, then she did the right thing. As it was, even the OP says that it was handled sensitively and he didn't feel offended. So I guess, all is well that ends well, and FTers beware.....