Nanoer, I really empathize with you. When I first started playing VMK I, too, got taken in a trade that I had not checked out thoroughly before accepting. I reported my "bad scam" trade, and a couple months later vmk sent me an email saying they would do nothing because I received something in trade for what I offered. This was before VMK put in the extra accept window for trades. Anyway, in the future ALWAYS take the time to go see if an item is available in the shops before trading for it, IF you are not 100% sure. If the trader really is honest, they will wait for you.
Do you have a spacesuit so you can go check out the inner-space shop for the specials? In case you or others do not, here is a list of what is there under specials:
Captain Nemo's chair color blue - 500 credits
Deep Sea diver helmet - 2000 credits
Flying saucer chair color light blue - 100 credits
Flying saucer chair color orange - 100 credits
Quest Kiosk - 30000 credits