Doesn't matter if he sold it or not. It was clearly his account, the current user hasn't proven that he acquired it with the consent of its owner, the owner has reported it stolen, and it was used for deceptive marketing by the current user.
Of course it matters. If you sold me a bike, I bought it and paid for it and then a year later you call the cops and tell them I stole your bike what do you think would happen. They would just give it back to you?
What if I could prove I had the bike for a year, and showed them pictures with you and me and the bike always with me riding it and parked in my garage.
Its the same thing here. Dont you understand or are you just a paid troll here to fud for cheap coins?
You cant sell something to someone and then claim you lost it or it got hacked or whatever.
Thats not how it works.
That is why you get a bill of sale, or a receipt, or some kind of proof of the transaction, when you purchase something. Otherwise, as you have pointed out, you have no proof of ownership if the seller later reports it stolen.