Sorry, I missed responding to your comment here.

if it's simply impossible for me to know if the funds are stolen or not?

It is not impossible. Do you do KYC on the seller? Considering you were getting a 30% discount and buying an account in an unusual way (and if you had seen the latest EOS news about many hacked accounts out there), then maybe you can take some responsibility for this?

how do you know a good is stolen?

By doing due diligence. As they say "Buyer beware."

Is giving your private keys to somebody mean that the other person stole your goods or did you give it to them?

If you're referring to the original account that got hacked, my understanding is a fraudulent website was involved that lied about key creation. Yes, the original person should not have trusted a shady website, but I also think the real bad actor was the thief who was rewarded through a sale with you.

Knowing who you do business with matters. That's how we can create a society we all want to live in. If the point of blockchain is just immutability without any connection to improving human well being than what's the point? You can trust the cryptographic realities of a transfer, but not the human beings who are initiating the transfers to begin with. That takes human intuition and involvement and is the whole reason EOS governance makes sense.

I really am curious to see what happens in this case and if ECAF can do anything further to help you. I assume you filed a claim as well?