I got in touch with the seller, it's a shame I had to post in here because somebody might connect the dots and it would put a user in a bad light.
I have removed headset at the bike shop, unfortunately, it's a crack, not a scratch. It's a shame as it's crazy light and beautiful frame. It took a good half an hour to figure out how to take pictures to make the crack visible from the top. Finally, I had to reach for such sophisticated technology as taking a picture with a phone via analog camera lens.
EDIT: I feel like I should update all the information about this case here so it won't cause any bad reputation for the seller. We just exchanged mails and I was promised full refund. Any tips how to help with potential insurance claim for the seller?