From AM Terms of Service:
BUYER BEWARE - YOU TAKE THE RISK.
Astromart is not involved in any transaction between any party who uses our site. There are risks that you assume when dealing with people who might be acting under false pretenses; all of these risks are borne by you. Astromart™ is a venue only and we do not screen or censor or otherwise control the classified listings offered to other Users, nor does Astromart screen or censor or otherwise control the Users of its service. Astromart cannot and does not control the behavior of the participants on this site. We cannot control whether or not Users of the Service will complete the transactions they describe on our site. IT IS EXTREMELY IMPORTANT THAT YOU USE CARE THROUGHOUT YOUR DEALINGS WITH OTHER PEOPLE ON THIS SITE!
DISPUTES & RELEASE.
If there is a dispute between participants on this site, Astromart is under no obligation to become involved. In the event that you have a dispute with one or more Users, you hereby release Astromart, its officers, employees, agents and successors in rights from claims, demands and damages (actual and consequential) of every kind or nature, known or unknown, suspected and unsuspected, disclosed and undisclosed, arising out of or in any way related to such disputes and/or our service.
So, other than posting on their forum to warn others (who read the forum), seems there's no recourse.