But how? I get that he did a face to face trade with a person he knew and got the bitcoins from him at a discount.
But how can the bitcoins be stolen if the person was holding it in his wallet ? except if the bitcoins were not truly hold in his non-custodial wallet.
There's something missing here and it doesn't make sense until we get to know how exactly he lost his coins.
The seller obtained the bitcoin through illegal means and deposited it into his wallet, then sold it to the buyer at a lower price than the market rate to make the deal more attractive. Later, the police went after the buyer because the source of the bitcoins was suspicious after he deposited it into a CEX..
I don't see anything illogical in what happened, and it can happen to anyone. Therefore, it is the responsibility of each person to verify the source of the Bitcoin they purchase, and to rely on trusted exchanges for buying rather than peer-to-peer deals. The Bitcoin may have been acquired through illegal means such as theft, hacking, or similar activities.