Proof of Payment

What is Proof of Payment (PoP)?

When you pay an invoice you receive a secret number represented by an hexadecimal string in your wallet, this is sent by the recipient of the coins, that number is your proof of payment, also known as preimage.

If you have positive balance but lost your cookie session you can recover your winnings just entering your preimage, here you can see how identify it using Bitcoin Lightning Wallet and Eclair Wallet .