It's probable that your PayPal buyer was actually using a stolen/hacked PayPal account, so as soon as the legitimate account holder realized a payment had been made from their account without their involvement, they contacted PayPal to dispute the unauthorized payment.
If you want to impede access to your actual product for such fraudulent buyers, you might consider redirecting to a Common Thank-you Page URL on your site (in Seller Admin > Account Preferences), so buyers would be unable to claim their download immediately following checkout and would need to wait to receive a thank-you email with a link to their E-junkie-generated thank-you page with download links. Thus, if a buyer using a hacked PayPal account does not also have access to the actual email inbox account for that PayPal Email address, they would be unable to obtain the download.