Interesting to see just how much people don't know how the state police forces operate. What Peter says is correct & sweetap you were very fortunate.
Do not think that you know how easy it is to investigate this sort of crime, jurisdictions DO affect how and where the investigation starts & finishes. Federal police will only look at it once it reaches a certain monetary value and or if it is media worthy or exceptional circumstances exist. This IS the same for drugs and other contraband. Customs even have a hard time getting them to look at dodgy importers.
Also, Gumtree is vastly worse than
ebay. (!!)
As in my previous post, direct your attention at
ebay. Not the police. I also said this forum does a great job identifying & reporting these people & should continue to do so regardless of any external difficulties.