@ElijahHu
Email that 'wrong' email address as it obviously belongs to someone and request a refund.
If they refuse and you sent it using the goods/services option then open a dispute for non receipt of item (as they have nothing to send you).
If you sent is using friends / family then your only option would be to contact your card issuer if you funded your paypal payment that way and request that they chargeback for you BUT they may decline as it was not a purchase for goods with that person.
Advice is voluntary.
Kudos / Solution appreciated.
