Affiliate Marketing Secrets

I sold an old computer to a person I didn’t know. Even though I deleted all my files, I later received an email from the person I sold the computer to that some files with sensitive information were recovered on the computer, and that the computer was currently listed in an auction on eBay. I asked him if I could buy the computer back from him, but he refused. As a result, I had to go on eBay and keep bidding higher in order to get my computer back (I ended up paying more than double what I sold it for). I know it was stupid of me to not overwrite my files (I’ll never make that mistake again), but is there any legal liability for the eBay auction seller? This feels like blackmail, but the person never threatened to expose any secrets or anything like that. Is the threat implied in the notice that he found the sensitive data? Is there anything I can do about it other than chalk up the loss to a lesson learned? I don’t know if that seller has done a similar thing to other people, but I definitely had to pay much more than a fair market price to get my laptop back.