>you aren't guilty of a crime unless you know that the goods actually are stolen.

Unless you're in a jurisdiction where the knowledge element can be satisfied by whether a reasonable person would suspect that the property was stolen. In that case you could be found guilty.

Which thankfully, does not apply to criminal charges in America. Where an intent element of "knowledgeable" must be proved, it must be proved that the specific individual knew, or should have known X. "Should have known" is a catch-some for people who willfully ignore what's going on right in front of them, but it does not encompass what a reasonable person would have suspected.

You're confusing the standards applicable to tort law (another person sues you for damages) or regulatory infractions (government sues you for money) with criminal law (government tries to send you to jail/prison).

On a separate note (by reading your comment), isn't funny how you need to be lawyer in order to find out whether you are breaking the law or no for trivial things as this one.

USSR perfected that approach but we are getting there.

You don't need to be a lawyer to know whether you are breaking the law for something like this. It's very simple: Are you trying to buy stuff? --> You're okay, unless... Are you trying to buy stuff that you know is stolen? --> That's a crime.