I agree not much can be done, unfortunately. But the buyer/seller rating system seems to have worked previously, as other members have stated.
However, age shouldnt matter at all. Anyone of any age can blow someone off, or no show.
I've also read that you can actually put your rock in a bucket and fill it with dechlorinated freshwater and the worm should come crawling out quickly after. Only downfall is the potential die off on the rock with the freshwater dip.
Haven't actually done this myself tho.