Car is sold and reg of the vehicle remains unchanged by chance and?
Indeed thats a problem but if Im understanding the timeline of your situation correctly, thats not your problem. Thats the sellers. Where this kind of stuff gets tricky is if the party before you never registered the vehicle your district has no record of them. In the USA we call it, skipping title. In theory your district may have safeguards in place to protect you. Id try and find out what those are from your local government office or district office where vehicle registrations/licensing is handled. Fines/penalties follow the owner not the VIN number. Investigate the processes to unravel that mess at either of the offices I mentioned.