You probably still have a PayPal account. If your buyer has one as well, you could try PayPal's "Send Money" function.
If you're both in Canada, an Interac eTransfer would work, too.
Both, of course, would involve some (but not a lot of) effort to get some information from the buyer.
If you're wanting some sort of "electronic paper trail" for the sale, though, you may have to suggest to your buyer that they file a case with PayPal, if they paid that way. They have up to 180 days from purchase date to do so.