Seems the buyer was aware of how eChecks work and took advantage of a loophole - the buyer did not have a backup funding source so he or she was able to choose the eCheck funding option. As the funds came from the buyer's bank account, after the eCheck was sent, the buyer then contacted his or her bank and requested that eCheck payment be cancelled - basically the buyer cannot cancel it directly but, the bank can if requested.
Here's the details from one of the FAQs:
An eCheck is an electronic payment funded by the buyer’s bank account. With an eCheck, the recipient should receive the money within 3-6 business days.
Both eChecks and Instant Transfers are ways to pay with your bank account. With an Instant Transfer, the recipient receives the money right away. You only need to have a confirmed U.S. bank account to send an eCheck, but an Instant Transfer also requires a backup funding source such as a credit or debit card registered on your PayPal account.
For buyers:
Before you make a payment, make sure you have enough money in your bank account to cover the eCheck. If there’s not enough money in your bank account, the bank will decline the payment and PayPal will represent it a second time.
You cannot send an eCheck if the Instant Transfer option is available. eChecks cannot be partially funded by a PayPal balance, so the full amount will always be requested from your bank.
If you’d like to cancel an eCheck after it’s issued, please call your bank. If you’d like to cancel an eCheck that has already cleared, please contact the seller directly to request a refund.
For sellers:
If you are issuing a refund and don’t have sufficient funds available in your PayPal balance, an eCheck with the full refund amount will be issued. Note that an eCheck for the full amount will always be requested from your bank, since eChecks cannot be partially funded by a PayPal balance.
