Seller cancelled auction immediately after end

I bid on a used Nintendo 3DS this afternoon - with an hour to go no one else had bid on the item and it was a good price. I won the auction and went to send the money, went through checkout but after hitting pay it told me (a) that the auction had been cancelled by the seller, and (b) that the stated reason for this was "buyer requested cancellation". I did no such thing! The item was back up for sale on a new auction within minutes (at the same starting price). I've messaged the seller a few times using 'contact the seller' on the new item listing but have had no reply. I've asked the AI agent under the help tab about this, who says this might be an abuse of the cancellation policy and if I report him they'll investigate, but even if they do they won't inform me of the outcome! So - is this a common shady practice, or have I been unlucky? I've been an ebay user for 22 years with almost a thousand positive feedbacks so I'm not wet behind the ears, but I've never come across this before